In simple words it is a pattern of symbol and characters. Regular expression is used to search,replace or modify the words/strings. It is the most important part of your daily programming usage whether rewriting url using .htaccess, form validation, validating user input etc.
Regular expression is a sequence of characters and each characters has it’s special meaning. Let’s look at some basic characters and it’s meaning.
Is your wordpress categories and tags pages get indexed. Learn how to deindex categories and tags pages of your wordpress blog from search engines.
If you are working on PHP, then definitely you are familiar with Fatal Error Allowed memory size exhausted. This error occurs when your PHP script exceeds the default memory allocated for execution. Due to which your scripts stop working and shows the error message that allowed memory size exhausted.
To know the default memory allocated for execution, you can check the memory limit in your php.ini file.