PHP strpos and substr functions causes 'Allowed memory size exhausted' error

Question

The part of my code is the following:

while( $pos1 = stripos( $description, '<style' ) ) {
  $pos2 = stripos( $description, '</style>' ) + 8;
  $description = substr( $description, 0, $pos1 ).
                 substr( $description, $pos2 );     //   <= This string causing the error
}

Sometimes (not all the time!) I receiving the error:

Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 107663188 bytes) in /path/to/my/script.php on line 88

88'th line indicated by the '<=' arrow above.

The size of $description variable is about 100 kB's. Besides I don't see any reason to believe that this code can cause accumulation of memory allocation without to be released.

Do you see any flaws in my code?

Answer 1

This code causes memory error

$description = 'hello<style></style>hello<style>';
while( $pos1 = stripos( $description, '<style' ) ) {
    $pos2 = stripos( $description, '</style>' ) + 8;
    $description = substr( $description, 0, $pos1 ).
        substr( $description, $pos2 );     //   <= This string causing the error
}

Answer 2

Looks like the problem caused by the fact that if </stile> is not find - the $description variable will grow up to infinity. This can appear if the <script> tag used in form <script ... /> Now the code is the following:

while( $pos1 = stripos( $description, '<style' ) ) {
  $pos2 = stripos( $description, '</style' ) + 8;
  if( $pos2 < $pos1 ) $pos2 = strpos( $description, '/>' ) + 2;
  if( $pos2 < $pos1 ) break 2;
  $description = substr( $description, 0, $pos1 ).
                 substr( $description, $pos2 );
}

Looks like there are no errors anymore...