How can lookbehind-assertion be used in PHP regular expressions?

Lookbehind assertion in PHP regular expressions allows you to match a pattern only if it is preceded by another pattern. This can be useful when you want to find a specific pattern only if it is preceded by a certain condition. To use lookbehind assertion in PHP, you can use the syntax `(?<=...)` where `...` is the pattern that should precede the main pattern you are trying to match. Example: 

$string = &quot;The price is $50. The discount is $10.&quot;;
$pattern = &#039;/(?&lt;=\$)\d+/&#039;; // Match digits preceded by a dollar sign
preg_match_all($pattern, $string, $matches);

print_r($matches[0]); // Output: Array ( [0] =&gt; 50 [1] =&gt; 10 )

Keywords

lookbehind assertion PHP regular expressions regex syntax

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