Programming PHP, 3rd Edition

Manipulating and Searching Strings

PHP has many functions to work with strings. The most commonly used functions for searching and modifying strings are those that use regular expressions to describe the string in question. The functions described in this section do not use regular expressions—they are faster than regular expressions, but they work only when you’re looking for a fixed string (for instance, if you’re looking for "12/11/01" rather than “any numbers separated by slashes”).

Substrings

If you know where the data that you are interested in lies in a larger string, you can copy it out with the substr() function:

$piece = substr(string, start [, length ]);

The start argument is the position in string at which to begin copying, with 0 meaning the start of the string. The length argument is the number of characters to copy (the default is to copy until the end of the string). For example:

$name  = "Fred Flintstone";
$fluff = substr($name, 6, 4);  // $fluff is "lint"
$sound = substr($name, 11);    // $sound is "tone"

To learn how many times a smaller string occurs in a larger one, use substr_count():

$number = substr_count(big_string, small_string);

For example:

$sketch = <<< EndOfSketch
Well, there's egg and bacon; egg sausage and bacon; egg and spam;
egg bacon and spam; egg bacon sausage and spam; spam bacon sausage
and spam; spam egg spam spam bacon and spam; spam sausage spam spam
bacon spam tomato and spam;
EndOfSketch;
$count = substr_count($sketch, "spam");
print("The word spam occurs ...