Parse, int. In real-world PHP programs we will often end up with a string containing digits in the form of a number. These strings are not ints, but can be converted to ints.
With the int cast, we can directly perform this conversion. Other approaches, like intval, also work. And is_numeric can tell us whether the cast will succeed.
Example. This example performs string to integer conversions in a variety of ways. It uses casts, intval, and the is_numeric function to test string data.
Part 1 We have the string containing 3 characters "100" and we cast it to an int with the int cast. This gives us the int 100.
Part 2 Sometimes PHP will perform the conversion on its own (an implicit cast). If we add 1 to the string "100", the string is converted to 100.
Part 3 If our string does not contain digits, using the int cast will return the int value 0.
Part 4 We can use the intval() function instead of an int cast to perform the string to int conversion.
Part 5 Floats have a decimal place and contain fractional numbers. The float cast can parse strings containing floats.
Part 6 We can test our string with is_numeric, which will tell us whether the int cast is appropriate to use.
// Part 1: convert numeric string to int.
$value = "100";
$test = (int) $value;
var_dump($value, $test);
// Part 2: add 1 to numeric string.
$value = "200";
$test = $value + 1;
var_dump($test);
// Part 3: if not numeric string, casting to int returns 0.
$value = "bird";
$test = (int) $value;
var_dump($test);
// Part 4: use intval to convert to integer.
$value = "300";
$test = intval($value);
var_dump($test);
// Part 5: convert string to float.
$value = "1.5";
$test = (float) $value;
var_dump($value, $test);
// Part 6: use is_numeric to determine if string is numeric, and then parse it.
$value = "600";
if (is_numeric($value)) {
$test = (int) $value;
var_dump($test);
}string(3) "100"
int(100)
int(201)
int(0)
int(300)
string(3) "1.5"
float(1.5)
int(600)
By using casts, we can change the type of strings to ints. If the cast does not succeed, the value 0 is returned—but we can use is_numeric to test for valid input.
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