Why Does preg_match Throw an 'Unknown Modifier 'g'' Error in PHP?

Understanding the "Unknown Modifier 'g' in...'' Error When Using preg_match in PHP

When utilizing the preg_match function in PHP, you may encounter the "Unknown modifier 'g'" error message. This perplexing issue can arise when attempting to use the 'g' modifier in regular expressions.

The 'g' modifier in regular expressions is typically employed for global search to find all occurrences of a pattern within a string. However, when used in conjunction with preg_match, this modifier is unrecognized. The reason behind this discrepancy stems from an oversight in PHP's implementation, as preg_match only supports the 'i' and 'm' modifiers.

To resolve this issue and perform a global search with preg_match, you should utilize the preg_match_all function instead. This function extends the functionality of preg_match by matching all occurrences of a pattern within a string, providing the desired global search functionality.

Therefore, to correct the code snippet you provided and perform a global search, modify the line containing the preg_match function to use preg_match_all:

preg_match_all("/^(\w|\.|-)+?@(\w|-)+?\.\w{2,4}($|\.\w{2,4})$/im", ....)

By utilizing preg_match_all with the appropriate modifiers, you can successfully find all occurrences of the email address pattern within your string, avoiding the "Unknown modifier 'g' in...'' error message.

The above is the detailed content of Why Does preg_match Throw an 'Unknown Modifier 'g'' Error in PHP?. For more information, please follow other related articles on the PHP Chinese website!