Introduction to knowledge about PHP associative arrays_PHP tutorial

The

function can make our code very simple. I have read a lot of PHP-related knowledge recently. Here I will introduce to you the knowledge about PHP associative arrays. Description international extract(array $var_array [ abstract $extract_type = EXTR_OVERWRITE [ , string $prefix] ] ) Imports the variable array into the current symbol table. Each key is checked to see if it has a legal variable name.

It also checks for collisions with existing variable symbol tables, PHP associative arrays. This function takes the key as the variable name and the value as the variable's value. For each key/value pair, a variable will be created in the current symbol table, subject to the extract_type and prefix parameters. You must use associative arrays, a numerically indexed array will not produce results unless you use EXTR_PREFIX_ALL or EXTR_PREFIX_INVALID.

The way invalid/numeric keys and collisions are treated is by extract_type. It can be one of the following values:
◆EXTR_OVERWRITE If there is a collision, overwrite the existing variable.
◆EXTR_SKIP If there is a collision, do not overwrite existing variables.
◆EXTR_PREFIX_SAME The prefix of the variable name if there is a collision.
◆The prefix of all variable names prefixed by EXTR_PREFIX_ALL.
◆EXTR_PREFIX_INVALID only prefixes the variable names with invalid/numeric prefixes.
◆EXTR_IF_EXISTS only overwrites the variable if it already exists in the current symbol table, otherwise, does nothing. It is helpful to define a list of valid variables and then extract only those variables you defined in the $_REQUEST array.
◆EXTR_PREFIX_IF_EXISTS only creates prefixed variable names if a non-prefixed version of the same variable exists in the current symbol table.
◆Reference of EXTR_REFSextract variable. This effectively means that the values ​​imported still refer to the value of the variable, the var_array parameter. You can use this flag by itself or in combination with any other flag OR'ing the extract_type.

If extract_type is not specified, EXTR_OVERWRITE is assumed. Note that the prefix is ​​only required if the extract_type is EXTR_PREFIX_SAME, EXTR_PREFIX_ALL, EXTR_PREFIX_INVALID or EXTR_PREFIX_IF_EXISTS. If the prefix result is not a valid variable name, it is not imported into the symbol table. An outstanding feature of prefixes is the automatic detachment of array keys. Returns some variables successfully imported into the symbol table. Release Notes 4.3.0 EXTR_REFS increased. 4.2.0 EXTR_IF_EXISTS and EXTR_PREFIX_IF_EXISTS were added. 4.0.5 This function now returns some variables extracted. EXTR_PREFIX_INVALID increases. EXTR_PREFIX_ALL includes numeric variables as well.

PHP associative array instance

Example: example of extract()

One possibility for extract() is to import into symbol Table variable containing associative array returned by wddx_deserialize().

<ol class="dp-xml">
<li class="alt"><span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">php</span></font></strong><span> </span></span></li>
<li class=""><span> </span></li>
<li class="alt"><span>/* Suppose that $var_array is an array returned from  </span></li>
<li class=""><span>wddx_deserialize */  </span></li>
<li class="alt"><span> </span></li>
<li class="">
<span>$</span><span class="attribute"><font color="#ff0000">size</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">"large"</font></span><span>;  </span>
</li>
<li class="alt">
<span>$</span><span class="attribute"><font color="#ff0000">var_array</font></span><span> = array("color" =</span><span class="tag"><strong><font color="#006699">></font></strong></span><span> "blue",  </span>
</li>
<li class="">
<span>"size"  =</span><span class="tag"><strong><font color="#006699">></font></strong></span><span> "medium",  </span>
</li>
<li class="alt">
<span>"shape" =</span><span class="tag"><strong><font color="#006699">></font></strong></span><span> "sphere");  </span>
</li>
<li class=""><span>extract($var_array, EXTR_PREFIX_SAME, "wddx");  </span></li>
<li class="alt"><span>echo "$color, $size, $shape, $wddx_sizen";  </span></li>
<li class="">
<span></span><span class="tag"><strong><font color="#006699">?></font></strong></span><span> </span>
</li>
</ol>

http://www.bkjia.com/PHPjc/446488.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446488.htmlTechArticle function can make our code very simple. I have read a lot of PHP related knowledge recently, and I will introduce it to you here. Learn about PHP associative arrays. describe international extract(array $var...