var_dump

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本文详细介绍了 PHP 中用于变量信息展示的 var_dump 函数，包括其语法、参数说明及返回值，通过示例展示了如何使用该函数查看数组、浮点数及布尔值等不同类型变量的结构与内容。

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var_dump

(PHP 4, PHP 5)

var_dump — Dumps information about a variable

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Description

void var_dump ( mixed $expression [, mixed $... ] )

This function displays structured information about one or more expressions that includes its type and value. Arrays and objects are explored recursively with values indented to show structure.

In PHP 5 all public, private and protected properties of objects will be returned in the output.

Tip

As with anything that outputsits result directly to the browser, the output-control functions can be used to capturethe output of this function, and save it in astring (for example).

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Parameters

expression

The variable you want to export.

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Return Values

No value is returned.

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Examples

Example #1 var_dump() example

<?php
$a = array(1, 2, array("a", "b", "c"));
var_dump($a);
?>

The above example will output:

array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  array(3) {
    [0]=>
    string(1) "a"
    [1]=>
    string(1) "b"
    [2]=>
    string(1) "c"
  }
}

<?php

$b = 3.1;
$c = true;
var_dump($b, $c);

?>

The above example will output:

float(3.1)
bool(true)