So, if preg_match results in int(0) you seem to have to check preg_last_error() if maybe an error occurred. In short, preg_match seems to return an int(0) instead of the expected boolean(false) if the regular expression could not be executed due to the PCRE recursion-limit. Here, the problem is that preg_match does not return boolean(false) as expected by the description / manual of above. On one of our Windows-Servers the above example does not crash PHP, but (directly) hits the recursion-limit. It wraps the possibly crashing preg_match call by decreasing the PCRE recursion limit in order to result in a Reg-Exp error instead of a PHP-crash. If you are looking for a work-around, the following code-snippet is what I found helpful. This seems to be a known bug (see ), but I don't know if it has been fixed, yet. On one of our Linux-Servers the above example crashes PHP-execution with a C(?) Segmentation Fault(!). In most cases, the following example will show one of two PHP-bugs discovered with preg_match depending on your PHP-version and configuration. If you're wondering why all the non-capturing subpatterns (which look like this "(?:", it's so that we can do this: It's not perfect, but it should work for most non-idealists. Here's one that we use that's pretty nifty. I see a lot of people trying to put together phone regex's and struggling (hey, no worries.they're complicated). Matching a backslash character can be confusing, because double escaping is needed in the pattern: first for PHP, second for the regex engine The numbering of the nodes in simplexml starts from zero, but from 1 in DOM xpath objects Here is a function that decreases the numbers inside a string (useful to convert DOM object into simplexml object)Į.g.: decremente_chaine("somenode->anode->achildnode") will return "somenode->anode->achildnode" When using the extended regular expression, do not escape the | operator:įor more information about how to build regular expressions, check out our Grep regex article.Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Enumerations Errors Exceptions Fibers Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Predefined Attributes Context options and parameters Supported Protocols and Wrappers Security Introduction General considerations Installed as CGI binary Installed as an Apache module Session Security Filesystem Security Database Security Error Reporting User Submitted Data Hiding PHP Keeping Current Features HTTP authentication with PHP Cookies Sessions Dealing with XForms Handling file uploads Using remote files Connection handling Persistent Database Connections Command line usage Garbage Collection DTrace Dynamic Tracing Function Reference Affecting PHP's Behaviour Audio Formats Manipulation Authentication Services Command Line Specific Extensions Compression and Archive Extensions Cryptography Extensions Database Extensions Date and Time Related Extensions File System Related Extensions Human Language and Character Encoding Support Image Processing and Generation Mail Related Extensions Mathematical Extensions Non-Text MIME Output Process Control Extensions Other Basic Extensions Other Services Search Engine Extensions Server Specific Extensions Session Extensions Text Processing Variable and Type Related Extensions Web Services Windows Only Extensions XML Manipulation GUI Extensions Keyboard Shortcuts ? This help j Next menu item k Previous menu item g p Previous man page g n Next man page G Scroll to bottom g g Scroll to top g h Goto homepage g s Goto search To interpret the pattern as an extended regular expression, invoke grep the -E option (or –extended-regexp). That’s why we’re escaping the OR operator (|) with a slash. To retain the special meanings of metacharacters, they must be escaped with a backslash (). When using basic regular expressions, metacharacters are interpreted as literal characters. The syntax for searching multiple patterns using the basic grep regular expressions is as follows:Īlways enclose the regular expression in single quotes to avoid the shell’s interpretation and expansion of metacharacters. This operator has the lowest precedence of all regular expression operators. The toggle operator | (pipe) allows you to specify different possible matches which can be literal strings or sets of expressions. To search for multiple patterns, use the OR (toggle) operator. When no regular expression type is specified, grep interprets search patterns as basic regular expressions. GNU grep supports three regular expression syntaxes, Basic, Extended and Perl compatible.
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