is_numeric function to check a numeric number in PHP

Check whether a value is numeric

is_numeric() accepts integers, floats and numeric strings, including supported scientific notation. Use it when numeric strings are acceptable; use integer validation when only whole numbers are valid.

$value = $_POST['amount'] ?? '';

if (is_numeric($value)) {
    $amount = (float) $value;
    echo 'Numeric value: ' . $amount;
} else {
    echo 'Enter a number.';
}

This is the recommended starting pattern. The detailed examples below are retained for explanation, comparison and related variations.

We can use is_numeric function in PHP to check if a number or variable is numeric or not. This function we can use to check user inputs of a form on a component where we expect only numeric data can be entered. This function can check and take care of decimal and exponential numbers also. Here is the syntax

is_numeric(number);

The above checking will return true or false based on the value stored on number. Let us try some examples. The output of each type of checking is given at its right side within comments.

echo is_numeric(12.35);// Output 1
echo "<br>";
echo is_numeric(.35);// Output 1
echo "<br>";
echo is_numeric(10e9);// Output 1
echo "<br>";
echo is_numeric(+11e-9)? "T" :"F";// Output T
echo "<br>";
echo is_numeric("05.050.1") ? "T" : "F";// Output F
echo "<br>";

$val=13.58;
echo is_numeric($val); // Output 1

We can also use FILTER_VALIDATE_INT php filter to validate integer.
If you are checking any form input then take care of left or right space and use trim function before applying is_numeric function.
ctype_digit() FILTER_VALIDATE_INT() is_int() intval(): Integer output
PHP Form ctype_alpha():Alphabetic chars only

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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is_numeric to validate number in php

Check whether a value is numeric

Subhendu Mohapatra