What are potential pitfalls or unexpected behaviors when using curly braces {} in regular expressions in PHP?

Using curly braces {} in regular expressions in PHP can lead to unexpected behaviors if not properly escaped. This is because curly braces are used to specify quantifiers in regular expressions, such as specifying a specific number of repetitions. To use curly braces as literal characters in a regular expression, they need to be escaped with a backslash (\) to avoid any interpretation as quantifiers. Example: 

// Incorrect usage of curly braces without escaping
$pattern = '/{/';

// Corrected usage with escaped curly braces
$pattern = '/\{/';

Keywords

PHP regular expressions curly braces unexpected behaviors pitfalls

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