I was trying to create a php code to parse some text and to process it.
I have difficult time with the substr (sub string), strpos (which return the position of a particular segment of string). Testing and debugging it is just a time consuming work.
Luckily my friend enlighten me by introducing me regular expression way to look for values in a text. Using regular expressions you can easy find a pattern in a string and/or replace it if you want.
BUT PHP regular expressions seems to be a quite complicated area especially when I am not a experienced Unix user.Historically regular expressions were originally designed to help working with strings under Unix systems.
The regular expressions basic syntax
To use regular expressions first you need to learn the syntax of the patterns. We can group the characters inside a pattern like this:
- Normal characters which match themselves like hello
- Start and end indicators as ^ and $
- Count indicators like +,*,?
- Logical operator like |
- Grouping with {},(),[]
An example pattern to check valid emails looks like this:
Code:^[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+.[a-zA-Z.]{2,5}$ The code to check the email using Perl compatible regular expression looks like this:
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$pattern = “/^[a-zA-Z0-9._-][email protected][a-zA-Z0-9-]+.[a-zA-Z.]{2,5}$/”;
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$email = “[email protected]”;