diff --git a/core/oql/build/PHP/LexerGenerator/Lexer.php b/core/oql/build/PHP/LexerGenerator/Lexer.php
index 8b1731d06..3d6833e3d 100644
--- a/core/oql/build/PHP/LexerGenerator/Lexer.php
+++ b/core/oql/build/PHP/LexerGenerator/Lexer.php
@@ -182,14 +182,14 @@ class PHP_LexerGenerator_Lexer
             $this->token = self::COMMENTEND;
             return true;
         }
-        if (preg_match('/\G%([a-z]+)/', $this->data, $token, null, $this->N)) {
+        if (preg_match('/\G%([a-z]+)/', $this->data, $token, 0, $this->N)) {
             $this->value = $token[1];
             $this->N += strlen($token[1]) + 1;
             $this->state = 'DeclarePI';
             $this->token = self::PI;
             return true;
         }
-        if (preg_match('/\G[a-zA-Z_][a-zA-Z0-9_]*/', $this->data, $token, null, $this->N)) {
+        if (preg_match('/\G[a-zA-Z_][a-zA-Z0-9_]*/', $this->data, $token, 0, $this->N)) {
             $this->value = $token[0];
             $this->token = self::PATTERN;
             $this->N += strlen($token[0]);
@@ -216,7 +216,7 @@ class PHP_LexerGenerator_Lexer
         if ($this->data[$this->N] == '{') {
             return $this->lexCode();
         }
-        if (!preg_match("/\G[^\n]+/", $this->data, $token, null, $this->N)) {
+        if (!preg_match("/\G[^\n]+/", $this->data, $token, 0, $this->N)) {
             $this->error('Unexpected end of file');
             return false;
         }
@@ -242,7 +242,7 @@ class PHP_LexerGenerator_Lexer
         if ($this->data[$this->N] == '{') {
             return $this->lexCode();
         }
-        if (!preg_match("/\G[^\n]+/", $this->data, $token, null, $this->N)) {
+        if (!preg_match("/\G[^\n]+/", $this->data, $token, 0, $this->N)) {
             $this->error('Unexpected end of file');
             return false;
         }
@@ -406,7 +406,7 @@ class PHP_LexerGenerator_Lexer
         if ($this->data[$this->N] == '\'') {
             return $this->lexQuote('\'');
         }
-        if (preg_match('/\G%([a-zA-Z_]+)/', $this->data, $token, null, $this->N)) {
+        if (preg_match('/\G%([a-zA-Z_]+)/', $this->data, $token, 0, $this->N)) {
             $this->value = $token[1];
             $this->N += strlen($token[1]) + 1;
             $this->state = 'DeclarePIRule';
@@ -419,7 +419,7 @@ class PHP_LexerGenerator_Lexer
         if ($this->data[$this->N] == '"') {
             return $this->lexQuote();
         }
-        if (preg_match('/\G[a-zA-Z_][a-zA-Z0-9_]*/', $this->data, $token, null, $this->N)) {
+        if (preg_match('/\G[a-zA-Z_][a-zA-Z0-9_]*/', $this->data, $token, 0, $this->N)) {
             $this->value = $token[0];
             $this->N += strlen($token[0]);
             $this->token = self::SUBPATTERN;
diff --git a/core/oql/build/PHP/LexerGenerator/Parser.php b/core/oql/build/PHP/LexerGenerator/Parser.php
index 0362ebba2..005b80a72 100644
--- a/core/oql/build/PHP/LexerGenerator/Parser.php
+++ b/core/oql/build/PHP/LexerGenerator/Parser.php
@@ -33,17 +33,19 @@ class PHP_LexerGenerator_ParseryyToken implements ArrayAccess
         return $this->_string;
     }
 
-    function offsetExists($offset)
+    function offsetExists($offset): bool
     {
         return isset($this->metadata[$offset]);
     }
 
+	// Return type mixed is not supported by PHP 7.4, we can remove the following PHP attribute and add the return type once iTop min PHP version is PHP 8.0+
+	#[\ReturnTypeWillChange]
     function offsetGet($offset)
     {
         return $this->metadata[$offset];
     }
 
-    function offsetSet($offset, $value)
+    function offsetSet($offset, $value): void
     {
         if ($offset === null) {
             if (isset($value[0])) {
@@ -66,7 +68,7 @@ class PHP_LexerGenerator_ParseryyToken implements ArrayAccess
         }
     }
 
-    function offsetUnset($offset)
+    function offsetUnset($offset): void
     {
         unset($this->metadata[$offset]);
     }
@@ -278,7 +280,7 @@ class PHP_LexerGenerator_Parser#line 171 "Parser.php"
                     $match = false;
                     foreach ($yy_yymore_patterns[' . $this->token . '] as $index => $rule) {
                         if (preg_match(\'/\' . $rule . \'/' . $this->patternFlags . '\',
-                                ' . $this->input . ', $yymatches, null, ' . $this->counter . ')) {
+                                ' . $this->input . ', $yymatches, 0, ' . $this->counter . ')) {
                             $yymatches = array_filter($yymatches, \'strlen\'); // remove empty sub-patterns
                             if ($match) {
                                 if (strlen($yymatches[0]) > strlen($match[0][0])) {
@@ -350,7 +352,7 @@ class PHP_LexerGenerator_Parser#line 171 "Parser.php"
             $pattern . '\';' . "\n");
         fwrite($this->out, '
         do {
-            if (preg_match($yy_global_pattern,' . $this->input . ', $yymatches, null, ' .
+            if (preg_match($yy_global_pattern,' . $this->input . ', $yymatches, 0, ' .
              $this->counter .
                     ')) {
                 $yysubmatches = $yymatches;
@@ -408,7 +410,7 @@ class PHP_LexerGenerator_Parser#line 171 "Parser.php"
                         }
                         $yysubmatches = array();
                         if (preg_match(\'/\' . $yy_yymore_patterns[' . $this->token . '][1] . \'/' . $this->patternFlags . '\',
-                              ' . $this->input . ', $yymatches, null, ' . $this->counter .')) {
+                              ' . $this->input . ', $yymatches, 0, ' . $this->counter .')) {
                             $yysubmatches = $yymatches;
                             $yymatches = array_filter($yymatches, \'strlen\'); // remove empty sub-patterns
                             next($yymatches); // skip global match
diff --git a/core/oql/build/PHP/LexerGenerator/Parser.y b/core/oql/build/PHP/LexerGenerator/Parser.y
index cfa96d688..401f12e8e 100644
--- a/core/oql/build/PHP/LexerGenerator/Parser.y
+++ b/core/oql/build/PHP/LexerGenerator/Parser.y
@@ -187,7 +187,7 @@ require_once 'PHP/LexerGenerator/Exception.php';
                     $match = false;
                     foreach ($yy_yymore_patterns[' . $this->token . '] as $index => $rule) {
                         if (preg_match(\'/\' . $rule . \'/' . $this->patternFlags . '\',
-                                ' . $this->input . ', $yymatches, null, ' . $this->counter . ')) {
+                                ' . $this->input . ', $yymatches, 0, ' . $this->counter . ')) {
                             $yymatches = array_filter($yymatches, \'strlen\'); // remove empty sub-patterns
                             if ($match) {
                                 if (strlen($yymatches[0]) > strlen($match[0][0])) {
@@ -259,7 +259,7 @@ require_once 'PHP/LexerGenerator/Exception.php';
             $pattern . '\';' . "\n");
         fwrite($this->out, '
         do {
-            if (preg_match($yy_global_pattern,' . $this->input . ', $yymatches, null, ' .
+            if (preg_match($yy_global_pattern,' . $this->input . ', $yymatches, 0, ' .
              $this->counter .
                     ')) {
                 $yysubmatches = $yymatches;
@@ -317,7 +317,7 @@ require_once 'PHP/LexerGenerator/Exception.php';
                         }
                         $yysubmatches = array();
                         if (preg_match(\'/\' . $yy_yymore_patterns[' . $this->token . '][1] . \'/' . $this->patternFlags . '\',
-                              ' . $this->input . ', $yymatches, null, ' . $this->counter .')) {
+                              ' . $this->input . ', $yymatches, 0, ' . $this->counter .')) {
                             $yysubmatches = $yymatches;
                             $yymatches = array_filter($yymatches, \'strlen\'); // remove empty sub-patterns
                             next($yymatches); // skip global match
diff --git a/core/oql/build/PHP/LexerGenerator/Regex/Lexer.php b/core/oql/build/PHP/LexerGenerator/Regex/Lexer.php
index f21839d50..b34531694 100644
--- a/core/oql/build/PHP/LexerGenerator/Regex/Lexer.php
+++ b/core/oql/build/PHP/LexerGenerator/Regex/Lexer.php
@@ -110,7 +110,7 @@ class PHP_LexerGenerator_Regex_Lexer
         $yy_global_pattern = '/\G(\\\\\\\\)|\G([^[\\\\^$.|()?*+{}]+)|\G(\\\\[][{}*.^$|?()+])|\G(\\[)|\G(\\|)|\G(\\\\[frnt]|\\\\x[0-9a-fA-F][0-9a-fA-F]?|\\\\[0-7][0-7][0-7]|\\\\x\\{[0-9a-fA-F]+\\})|\G(\\\\[0-9][0-9])|\G(\\\\[abBGcedDsSwW0C]|\\\\c\\\\)|\G(\\^)|\G(\\\\A)|\G(\\))|\G(\\$)|\G(\\*\\?|\\+\\?|[*?+]|\\{[0-9]+\\}|\\{[0-9]+,\\}|\\{[0-9]+,[0-9]+\\})|\G(\\\\[zZ])|\G(\\(\\?)|\G(\\()|\G(\\.)|\G(\\\\[1-9])|\G(\\\\p\\{\\^?..?\\}|\\\\P\\{..?\\}|\\\\X)|\G(\\\\p\\{C[cfnos]?|L[lmotu]?|M[cen]?|N[dlo]?|P[cdefios]?|S[ckmo]?|Z[lps]?\\})|\G(\\\\p\\{\\^C[cfnos]?|L[lmotu]?|M[cen]?|N[dlo]?|P[cdefios]?|S[ckmo]?|Z[lps]?\\})|\G(\\\\p[CLMNPSZ])|\G(\\\\)/';
 
         do {
-            if (preg_match($yy_global_pattern,$this->input, $yymatches, null, $this->N)) {
+            if (preg_match($yy_global_pattern,$this->input, $yymatches, 0, $this->N)) {
                 $yysubmatches = $yymatches;
                 $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                 if (!count($yymatches)) {
@@ -180,7 +180,7 @@ class PHP_LexerGenerator_Regex_Lexer
                         }
                         $yysubmatches = array();
                         if (preg_match('/' . $yy_yymore_patterns[$this->token][1] . '/',
-                              $this->input, $yymatches, null, $this->N)) {
+                              $this->input, $yymatches, 0, $this->N)) {
                             $yysubmatches = $yymatches;
                             $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                             next($yymatches); // skip global match
@@ -360,7 +360,7 @@ class PHP_LexerGenerator_Regex_Lexer
         $yy_global_pattern = '/\G(\\^)|\G(\\])|\G(.)/';
 
         do {
-            if (preg_match($yy_global_pattern,$this->input, $yymatches, null, $this->N)) {
+            if (preg_match($yy_global_pattern,$this->input, $yymatches, 0, $this->N)) {
                 $yysubmatches = $yymatches;
                 $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                 if (!count($yymatches)) {
@@ -410,7 +410,7 @@ class PHP_LexerGenerator_Regex_Lexer
                         }
                         $yysubmatches = array();
                         if (preg_match('/' . $yy_yymore_patterns[$this->token][1] . '/',
-                              $this->input, $yymatches, null, $this->N)) {
+                              $this->input, $yymatches, 0, $this->N)) {
                             $yysubmatches = $yymatches;
                             $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                             next($yymatches); // skip global match
@@ -497,7 +497,7 @@ class PHP_LexerGenerator_Regex_Lexer
         $yy_global_pattern = '/\G(\\\\\\\\)|\G(\\])|\G(\\\\[frnt]|\\\\x[0-9a-fA-F][0-9a-fA-F]?|\\\\[0-7][0-7][0-7]|\\\\x\\{[0-9a-fA-F]+\\})|\G(\\\\[bacedDsSwW0C]|\\\\c\\\\|\\\\x\\{[0-9a-fA-F]+\\}|\\\\[0-7][0-7][0-7]|\\\\x[0-9a-fA-F][0-9a-fA-F]?)|\G(\\\\[0-9][0-9])|\G(\\\\[1-9])|\G(\\\\[]\.\-\^])|\G(-(?!]))|\G([^\-\\\\])|\G(\\\\)|\G(.)/';
 
         do {
-            if (preg_match($yy_global_pattern,$this->input, $yymatches, null, $this->N)) {
+            if (preg_match($yy_global_pattern,$this->input, $yymatches, 0, $this->N)) {
                 $yysubmatches = $yymatches;
                 $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                 if (!count($yymatches)) {
@@ -555,7 +555,7 @@ class PHP_LexerGenerator_Regex_Lexer
                         }
                         $yysubmatches = array();
                         if (preg_match('/' . $yy_yymore_patterns[$this->token][1] . '/',
-                              $this->input, $yymatches, null, $this->N)) {
+                              $this->input, $yymatches, 0, $this->N)) {
                             $yysubmatches = $yymatches;
                             $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                             next($yymatches); // skip global match
@@ -678,7 +678,7 @@ class PHP_LexerGenerator_Regex_Lexer
         $yy_global_pattern = '/\G(\\\\\\\\)|\G(\\\\\\])|\G(\\\\[bacedDsSwW0C]|\\\\c\\\\|\\\\x\\{[0-9a-fA-F]+\\}|\\\\[0-7][0-7][0-7]|\\\\x[0-9a-fA-F][0-9a-fA-F]?)|\G(\\\\[0-9][0-9])|\G(\\\\[1-9])|\G([^\-\\\\])|\G(\\\\)/';
 
         do {
-            if (preg_match($yy_global_pattern,$this->input, $yymatches, null, $this->N)) {
+            if (preg_match($yy_global_pattern,$this->input, $yymatches, 0, $this->N)) {
                 $yysubmatches = $yymatches;
                 $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                 if (!count($yymatches)) {
@@ -732,7 +732,7 @@ class PHP_LexerGenerator_Regex_Lexer
                         }
                         $yysubmatches = array();
                         if (preg_match('/' . $yy_yymore_patterns[$this->token][1] . '/',
-                              $this->input, $yymatches, null, $this->N)) {
+                              $this->input, $yymatches, 0, $this->N)) {
                             $yysubmatches = $yymatches;
                             $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                             next($yymatches); // skip global match
@@ -842,7 +842,7 @@ class PHP_LexerGenerator_Regex_Lexer
         $yy_global_pattern = '/\G([imsxUX]+-[imsxUX]+|[imsxUX]+|-[imsxUX]+)|\G(:)|\G(\\))|\G(P<[^>]+>)|\G(<=)|\G(<!)|\G(=)|\G(!)|\G(>)|\G(\\(\\?)|\G(#[^)]+)|\G(R)|\G(.)/';
 
         do {
-            if (preg_match($yy_global_pattern,$this->input, $yymatches, null, $this->N)) {
+            if (preg_match($yy_global_pattern,$this->input, $yymatches, 0, $this->N)) {
                 $yysubmatches = $yymatches;
                 $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                 if (!count($yymatches)) {
@@ -902,7 +902,7 @@ class PHP_LexerGenerator_Regex_Lexer
                         }
                         $yysubmatches = array();
                         if (preg_match('/' . $yy_yymore_patterns[$this->token][1] . '/',
-                              $this->input, $yymatches, null, $this->N)) {
+                              $this->input, $yymatches, 0, $this->N)) {
                             $yysubmatches = $yymatches;
                             $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                             next($yymatches); // skip global match
diff --git a/core/oql/build/PHP/LexerGenerator/Regex/Parser.php b/core/oql/build/PHP/LexerGenerator/Regex/Parser.php
index 4e1faf1fd..4c7876004 100644
--- a/core/oql/build/PHP/LexerGenerator/Regex/Parser.php
+++ b/core/oql/build/PHP/LexerGenerator/Regex/Parser.php
@@ -33,17 +33,19 @@ class PHP_LexerGenerator_Regex_yyToken implements ArrayAccess
         return $this->_string;
     }
 
-    function offsetExists($offset)
+    function offsetExists($offset): bool
     {
         return isset($this->metadata[$offset]);
     }
 
+	// Return type mixed is not supported by PHP 7.4, we can remove the following PHP attribute and add the return type once iTop min PHP version is PHP 8.0+
+	#[\ReturnTypeWillChange]
     function offsetGet($offset)
     {
         return $this->metadata[$offset];
     }
 
-    function offsetSet($offset, $value)
+    function offsetSet($offset, $value): void
     {
         if ($offset === null) {
             if (isset($value[0])) {
@@ -66,7 +68,7 @@ class PHP_LexerGenerator_Regex_yyToken implements ArrayAccess
         }
     }
 
-    function offsetUnset($offset)
+    function offsetUnset($offset): void
     {
         unset($this->metadata[$offset]);
     }
diff --git a/core/oql/oql-lexer.php b/core/oql/oql-lexer.php
index 3744c0742..42ca53cce 100644
--- a/core/oql/oql-lexer.php
+++ b/core/oql/oql-lexer.php
@@ -235,7 +235,7 @@ class OQLLexerRaw
                     $match = false;
                     foreach ($yy_yymore_patterns[$this->token] as $index => $rule) {
                         if (preg_match('/' . $rule . '/',
-                                $this->data, $yymatches, null, $this->count)) {
+                                $this->data, $yymatches, 0, $this->count)) {
                             $yymatches = array_filter($yymatches, 'strlen'); // remove empty sub-patterns
                             if ($match) {
                                 if (strlen($yymatches[0]) > strlen($match[0][0])) {