PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

106 Chapter 3 Using Arrays
Table 3.2
Type
Continued
Meaning
EXTR_PREFIX_IF_EXISTS
EXTR_REFS
Creates a prefixed version only if the nonprefixed version
already exists.
Extracts variables as references.
The two most useful options are EXTR_OVERWRITE (the default) and EXTR_PREFIX_ALL.
The other options might be useful occasionally when you know that a particular
collision will occur and want that key skipped or prefixed. A simple example using
EXTR_PREFIX_ALL follows.You can see that the variables created are called prefixunderscore-keyname:
$array = array( ‘key1’ => ‘value1’, ‘key2’ => ‘value2’, ‘key3’ => ‘value3’);
extract($array, EXTR_PREFIX_ALL, ‘my_prefix’);
echo “$my_prefix_key1 $my_prefix_key2 $my_prefix_key3”;
This code again produces the following output:
value1 value2 value3
Note that for extract() to extract an element, that element’s key must be a valid variable
name, which means that keys starting with numbers or including spaces are skipped.
Further Reading
This chapter covers what we believe to be the most useful of PHP’s array functions.We
have chosen not to cover all the possible array functions.The online PHP manual available
at http://www.php.net/array provides a brief description for each of them.
Next
In the next chapter, you learn about string processing functions.We cover functions that
search, replace, split, and merge strings, as well as the powerful regular expression functions
that can perform almost any action on a string.