php-regexHow to use quantifiers in PHP regex?

Quantifiers are used in PHP regex to specify the number of times a character, group, or character class must appear in the input string for a match to be found.

For example, the following code uses the quantifier + to match one or more occurrences of the letter a:

$string = 'aaabbb';
preg_match('/a+/', $string, $matches);

The output of the above code will be:

Array
(
    [0] => aaa
)

The following is a list of quantifiers and their meanings:

• ? - matches zero or one occurrence of the preceding character, group, or character class
• * - matches zero or more occurrences of the preceding character, group, or character class
• + - matches one or more occurrences of the preceding character, group, or character class
• {n} - matches exactly n occurrences of the preceding character, group, or character class
• {n,} - matches n or more occurrences of the preceding character, group, or character class
• {n,m} - matches at least n and at most m occurrences of the preceding character, group, or character class

Helpful links

• PHP Regex Quantifiers
• Regular Expressions Tutorial

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