¿Qué es una expresión regular en PHP?

What is a regular expression in PHP?

A regular expression is a sequence of characters that forms a search pattern. A regular expression can be a single character, or a more complicated pattern. Regular expressions can be used to perform all types of text search and text replace operations.

In most cases, the following example will show one of two PHP-bugs discovered with preg_match depending on your PHP-version and configuration. On one of our Linux-Servers the above example crashes PHP-execution with a C (?) Segmentation Fault (!).

Here, the problem is that preg_match does not return boolean (false) as expected by the description / manual of above. 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.

When trying to match accented characters, such as those found in Spanish, there seems to be a different internal interpretation when using character classes. So the best way is to add the u option (for unicode) after the delimiters. for those coming over from ereg, preg_match can be quite intimidating. to get started here is a migration tip.

The string must have 1 or more of any character like hyphen, letter, number, underscore, and may contain a slash or back slash at the end, to have a directory like (“/” or “folderName” or “folderName/”), this may be repeated one or more times.

A regular expression is a pattern match algorithm. Regular expressions are very useful when performing validation checks, creating HTML template systems that recognize tags etc. PHP has built in functions namely preg_match,preg_split and preg_replace that support regular expressions.

A regular expression, regex or regexp (sometimes called a rational expression) is a sequence of characters that define a search pattern. Usually such patterns are used by string searching algorithms for “find” or “find and replace” operations on strings, or for input validation.

Regex or Regular Expressions are an important part of Perl Programming. It is used for searching the specified text pattern. In this, set of characters together form the search pattern. It is also known as regexp.