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How do I convert a string to a number in PHP?

Nadia S.

The Problem

How do I convert a string to a number in PHP?

The Solution

We’ll take a look at four ways to convert numeric strings into numbers in PHP:

  • Dynamic typing.
  • The intval() and floatval() functions.
  • Type casting with (int) and (float).
  • The settype() function.

Dynamic Typing

PHP is a dynamically typed language that recognizes numerical strings. You can perform mathematical operations directly with numeric strings. When we add 5 to '3.14', we get a float of 8.14 as a result:

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$string = '3.14';
$mySum = $string + 5;

var_dump($mySum);

Output:

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// we get a float of 8.14
float(8.14)

The intval() and floatval() Functions

You can pass a numeric string literal into the intval() function to get the integer version or the floatval() function to get the float version. For example:

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// convert '3.9' to int and float
$myFloat = floatval('3.9');
$myInt = intval('3.9');

// echo out type and value
echo '$myFloat is ',var_dump($myFloat);
echo '$myInt is ',var_dump($myInt);

We get an output of 3.9 as our float value. Note how casting a number to an integer won’t round it off, as'3.9' becomes 3:

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$myFloat is float(3.9)
$myInt is int(3)

Type Casting with (int) and (float)

Make the (int) or (float) declaration in front of a numeric string literal to type cast it accordingly. For example:

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$castFloat = (float) '3.9';
$castInt = (int) '3.9';

echo '$castFloat is ',var_dump($castFloat);
echo '$castInt is ',var_dump($castInt);

Output:

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$castFloat is float(3.9)
$castInt is int(3)

The settype() Function

You can change the data type of the original numeric string into a float or integer using the settype() function. This is useful in cases where you don’t want to create a new variable to hold a value of a different data type.

In this example, we pass in the variable $pi and the datatype 'float' as arguments into the settype() function:

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$pi = '3.14';
settype($pi, "float");

var_dump($pi);

The $pi value is now a float.

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float(3.14)

Here we pass in 'integer' to change our $num variable to an integer:

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$num = '4.5';
settype($num, 'integer');

var_dump($num);

Output:

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int(4)

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