Add Special Characters to Patterns in PHP Scripts
Part of the PHP, MySQL, JavaScript & HTML5 All-in-One For Dummies Cheat Sheet
When you're working with PHP scripts, you sometimes need to compare character strings to see if they fit certain characteristics, rather than to see if they match exact values. For example, you might want to identify strings that begin with S or strings that have numbers in them. For this type of comparison, you compare the string to a pattern. These patterns are called regular expressions. Here's a reference sheet that includes some of the special characters that you'll use when creating patterns:
| Character | Meaning | Example | Match | Not a Match |
|---|---|---|---|---|
| ^ | Beginning of line | ^c | cat | my cat |
| $ | End of line | c$ | tic | stick |
| . | Any single character | .. | me, go | a |
| ? | Preceding item is optional | mea?n | mean, men | moan |
| ( ) | Groups literal characters | m(ea)n | mean | men,mn |
| [ ] | Any character in set | abc[1-3] | abc1,abc2 | abc4 |
| [^ ] | Any character not in set | m[!ea]n | min, mon | men, man |
| + | One or more | door[1-3]+ | door111, door131 | door, door55 |
| * | Zero or more | door[1-3]* | door, door311 | door4, door445 |
| { , } | Range of repetitions | a{2,5} | aa,aaaaa | a, xx3 |
| \ | Escapes character | m\*n | m*n | men, mean |
| ( | | ) | Alternate strings | (Tom|Tommy) | Tom, Tommy | Thomas, To |
