print_r
(PHP 4, PHP 5)
print_r — Prints human-readable information about a variable
說明
print_r() displays information about a variable in a way that's readable by humans.
print_r(), var_dump() and var_export() will also show protected and private properties of objects with PHP 5.
Remember that print_r() will move the array pointer to the end. Use reset() to bring it back to beginning.
參數
- expression
-
The expression to be printed.
- return
-
If you would like to capture the output of print_r(), use the return parameter. If this parameter is set to TRUE, print_r() will return its output, instead of printing it (which it does by default).
Return值
If given a string, integer or float, the value itself will be printed. If given an array, values will be presented in a format that shows keys and elements. Similar notation is used for objects.
註釋
Note: 該函式的內部依賴這個參數使用輸出緩衝，所以它不能在 ob_start() 的回呼(Callback)函式中使用
更新日誌
| 版本 | 說明 |
|---|---|
| 4.3.0 | The return parameter was added. If you need to capture the output of print_r() with an older version of PHP prior, use the output-control functions. |
| 4.0.4 | Prior to PHP 4.0.4, print_r() will continue forever if given an array or object that contains a direct or indirect reference to itself. An example is print_r($GLOBALS) because $GLOBALS is itself a global variable that contains a reference to itself. |
範例
Example#1 print_r() example
<pre>
<?php
$a = array ('a' => 'apple', 'b' => 'banana', 'c' => array ('x', 'y', 'z'));
print_r ($a);
?>
</pre>
上例將輸出：
<pre> Array ( [a] => apple [b] => banana [c] => Array ( [0] => x [1] => y [2] => z ) ) </pre>
Example#2 return parameter example
<?php
$b = array ('m' => 'monkey', 'foo' => 'bar', 'x' => array ('x', 'y', 'z'));
$results = print_r($b, true); // $results now contains output from print_r
?>