


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.
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<p> <?php </p> $a = array ('a' => 'apple', 'b' => 'banana', 'c' => array ('x','y','z'));</p>
?>
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<p> Array</p> (
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$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().
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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;
echo $v; |
*/
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().
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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... |

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Multiple calls to session_start() will result in warning messages and possible data overwrites. 1) PHP will issue a warning, prompting that the session has been started. 2) It may cause unexpected overwriting of session data. 3) Use session_status() to check the session status to avoid repeated calls.

Configuring the session lifecycle in PHP can be achieved by setting session.gc_maxlifetime and session.cookie_lifetime. 1) session.gc_maxlifetime controls the survival time of server-side session data, 2) session.cookie_lifetime controls the life cycle of client cookies. When set to 0, the cookie expires when the browser is closed.


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