Introduction to the usage of print_r, var_export and var_dump in PHP_PHP tutorial

The article introduces in detail the difference between print_r, var_export, and var_dump in PHP and the usage of these in different PHP applications. Friends in need can refer to it

It can be seen that both print_r and var_export can be used As a return value, you only need to set the second parameter to true

print_r
(PHP 4, PHP 5)print_r – Print human-readable information about variables.

Description
bool print_r (mixed expression [, bool return])

Note: The parameter return was added in PHP 4.3.0

print_r() displays easy-to-understand information about a variable. If a string, integer, or float is given, the variable value itself is printed. If an array is given, the keys and elements will be displayed in a certain format. object is similar to an array.

Remember, print_r() will move the array pointer to the end. Use reset() to return the pointer to the beginning.

The code is as follows

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代码如下	复制代码
<br> <?php<br /> $a = array ('a' => 'apple', 'b' => 'banana', 'c' => array ('x','y','z'));<br> print_r ($a);<br> ?><br>

<p>
<?php</p>
$a = array ('a' => 'apple', 'b' => 'banana', 'c' => array ('x','y','z'));</p>
<table width="620" align="center" border="0" cellpadding="1" cellspacing="1" style="background:#FB7">
	  <tr>
		<td width="464" height="27" bgcolor="#FFE7CE"> 代码如下</td>
		<td width="109" align="center" bgcolor="#FFE7CE" style="cursor:pointer;" onclick="doCopy('copy5083')">复制代码</td>
	  </tr>
	  <tr>
		<td height="auto" colspan="2" valign="top" bgcolor="#FFFFFF" style="padding:10px;" class="copyclass" id="copy5083">
<p><pre class="brush:php;toolbar:false"><br>
Array<br>
(<br>
    [a] => apple<br>
    [b] => banana<br>
    [c] => Array<br>
        (<br>
            [0] => x<br>
            [1] => y<br>
            [2] => z<br>
        )<br>
)<br>

print_r ($a);

?>

The above code will output:

The code is as follows

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<p> Array</p> (<table width="620" align="center" border="0" cellpadding="1" cellspacing="1" style="background:#FB7"> <tr> <td width="464" height="27" bgcolor="#FFE7CE"> 代码如下</td> <td width="109" align="center" bgcolor="#FFE7CE" style="cursor:pointer;" onclick="doCopy('copy7179')">复制代码</td> </tr> <tr> <td height="auto" colspan="2" valign="top" bgcolor="#FFFFFF" style="padding:10px;" class="copyclass" id="copy7179"> <p><?php<br /> $b = array ('m' => 'monkey', 'foo' => 'bar', 'x' => array ('x', 'y', 'z'));<br> $results = print_r ($b, true); //$results 包含了 print_r 的输出结果<br> ?>  <br>  </p> </td> </tr> </table> [a] => apple [b] => banana [c] => Array (                                                   [0] => x [1] = & gt; y                                                   [2] => z ) )

If you want to capture the output of print_r(), you can use the return parameter. If this parameter is set to TRUE, print_r() will not print the results (this is the default action), but will return its output. Example 1. Return parameter example

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$b = array ('m' => 'monkey', 'foo' => 'bar', 'x' => array ('x', 'y', 'z')); $results = print_r ($b, true); //$results contains the output results of print_r ?>

Note: If you want to capture the output of print_r() in versions prior to PHP 4.3.0, you can use the output control function.

Note: In versions prior to PHP 4.0.4, if the given array or object contained a direct or indirect reference to itself, print_r() would continue forever. print_r($GLOBALS) is an example, because $GLOBALS itself is a global variable, which contains a reference to itself.

var_export
(PHP 4 >= 4.2.0, PHP 5)var_export – Export or return a string representation of a variable

Description
mixed var_export ( mixed expression [, bool return])

This function returns structural information about the variable passed to the function. It is similar to var_dump(), except that the representation returned is legal PHP code.

You can return a representation of a variable by setting the second parameter of the function to TRUE.

Compare var_export() and var_dump().

The code is as follows

代码如下	复制代码
<br> <?php<br /> $a = array (1, 2, array ("a", "b", "c"));<br /> var_export ($a); /* 输出：<br /> array (<br /> 0 => 1,<br> 1 => 2,<br> 2 =><br> array (<br> 0 => 'a',<br> 1 => 'b',<br> 2 => 'c',<br> ),<br> )<br> */</p> <p>$b = 3.1;<br> $v = var_export($b, TRUE);<br> echo $v;</p> <p>/* 输出：<br> 3.1<br> */<br> ?><br>

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<p>
<?php<br />
$a = array (1, 2, array ("a", "b", "c"));</p>
var_export ($a); /* Output: <p>
array (<br />
0 => 1,</p>
1 => 2,<p>
2 =></p>
array (<p>
0 => 'a',</p>
1 => 'b',<p>
2 => 'c',</p>
),<p>
)</p>
*/<p>
</p>$b = 3.1;<table width="620" align="center" border="0" cellpadding="1" cellspacing="1" style="background:#FB7">
	  <tr>
		<td width="464" height="27" bgcolor="#FFE7CE"> 代码如下</td>
		<td width="109" align="center" bgcolor="#FFE7CE" style="cursor:pointer;" onclick="doCopy('copy4683')">复制代码</td>
	  </tr>
	  <tr>
		<td height="auto" colspan="2" valign="top" bgcolor="#FFFFFF" style="padding:10px;" class="copyclass" id="copy4683">
<p><pre class="brush:php;toolbar:false"><br>
<?php<br />
$a = array (1, 2, array ("a", "b", "c"));<br />
var_dump ($a); /* 输出：<br />
array(3) {<br />
[0]=><br>
int(1)<br>
[1]=><br>
int(2)<br>
[2]=><br>
array(3) {<br>
[0]=><br>
string(1) "a"<br>
[1]=><br>
string(1) "b"<br>
[2]=><br>
string(1) "c"<br>
}<br>
}*/</p>
<p> </p>
<p>$b = 3.1;<br>
$c = TRUE;<br>
var_dump($b,$c);</p>
<p>/* 输出：<br>
float(3.1)<br>
bool(true)*/</p>
<p>?><br>

$v = var_export($b, TRUE);

echo $v;

/* Output:

3.1 */ ?>

var_dump (PHP 3>= 3.0.5, PHP 4, PHP 5)var_dump – prints information about variables Description void var_dump (mixed expression [, mixed expression [, ...]]) This function displays structural information about one or more expressions, including the type and value of the expression. Arrays will recursively expand values, showing their structure through indentation.

Tip: To prevent the program from outputting results directly to the browser, you can use output-control functions to capture the output of the function and save them to a string variable. You can compare var_dump() and print_r().

Example 1. var_dump() example

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<?php<🎜> $a = array (1, 2, array ("a", "b", "c"));<🎜> var_dump ($a); /* Output: <🎜> array(3) {<🎜> [0]=> int(1) [1]=> int(2) [2]=> array(3) { [0]=> string(1) "a" [1]=> string(1) "b" [2]=> string(1) "c" } }*/ $b = 3.1; $c = TRUE; var_dump($b,$c); /* Output: float(3.1) bool(true)*/ ?> http://www.bkjia.com/PHPjc/631298.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/631298.htmlTechArticleThe article introduces in detail the difference between print_r, var_export and var_dump in PHP and the different applications of these in php Friends in need can refer to the usage in pr...