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在本文中，我们将介绍在 PHP 中将字符串转换为数字的方法。

• 使用显式类型转换
• 使用 intval()/floatval() 函数
• 使用 settype() 函数

在 PHP 中使用显式类型转换将字符串转换为数字

显式类型转换将任何类型的变量转换为所需类型的变量。它将变量转换为原始数据类型。将变量显式类型转换为 int 或 float 的正确语法如下

$variableName = (int)$stringName
$variableName = (float)$stringName

变量 $variableName 是整数变量，用于保存 number 的值。变量 $stringName 是数字字符串。我们还可以将非数字字符串转换为数字。

<?php  
$variable = "10";
$integer = (int)$variable;
echo "The variable $variable has converted to a number and its value is $integer.";  
echo "\n";

$variable = "8.1";
$float = (float)$variable;
echo "The variable $variable has converted to a number and its value is $float.";  
?>

输出：

The variable 10 has converted to a number and its value is 10.
The variable 8.1 has converted to a number and its value is 8.1.

对于非数字字符串，我们将得到 0 作为输出。

<?php  
$variable = "abc";
$integer = (int)$variable;
echo "The variable has converted to a number and its value is $integer.";  
?>

输出：

The variable has converted to a number and its value is 0.

在 PHP 中使用 intval() 函数将字符串转换为数字

intval() 函数将字符串转换为整型 int。

floatval() 函数将字符串转换为浮点数 float。

这些函数接受的参数是一个字符串，返回值分别是一个整数或一个浮点数。

intval( $StringName );  

变量 StringName 是字符串类型。

<?php  
$variable = "53";
$integer = intval($variable);
echo "The variable $variable has converted to a number and its value is $integer.";  
echo "\n";

$variable = "25.3";
$float = floatval($variable);
echo "The variable $variable has converted to a number and its value is $float.";  
?>

输出：

The variable 53 has converted to a number and its value is 53.
The variable 25.3 has converted to a number and its value is 25.3.

如果给定的字符串是数字和字符串表示形式的混合，例如 2020Time，则 intval() 将返回 2020。但是，如果给定的字符串不是以数字开头，则它将返回 0。floatval() 方法也是如此。

示例代码：

<?php  
$variable = "2020Time";
$integer = intval($variable);
echo "The variable $variable has converted to a number and its value is $integer.";  
echo "\n";

$variable = "Time2020";
$integer = intval($variable);
echo "The variable $variable has converted to a number and its value is $integer.";  
echo "\n";

$variable = "25.3Time";
$float = floatval($variable);
echo "The variable $variable has converted to a number and its value is $float.";  
echo "\n";

$variable = "Time25.3";
$float = floatval($variable);
echo "The variable $variable has converted to a number and its value is $float.";  
?>

输出：

The variable 2020Time has converted to a number and its value is 2020.
The variable Time2020 has converted to a number and its value is 0.
The variable 25.3Time has converted to a number and its value is 25.3.
The variable Time25.3 has converted to a number and its value is 0.

在 PHP 中使用 settype() 函数将字符串转换为数字

settype() 函数将任何数据类型的变量转换为特定数据类型。它接受两个参数，变量和类型名称。

settype($variableName, "typeName");

$variableName 是我们要转换为数字的任何数据类型的变量。"typeName" 是我们要为 $variableName 变量使用的数据类型的名称。

<?php  
$variable = "45";
settype($variable, "integer");
echo "The variable has converted to a number and its value is $variable.";  
?>

settype() 函数将 $variable 的类型从字符串设置为整型 integer。它仅适用于原始数据类型。

输出：

The variable has converted to a number and its value is 45.