How can I check if a char is a letter or a number?

Question

I have a string and I want to loop it so that I can check if every char is a letter or number.

$s = "rfewr545 345b";

for ($i=1; $i<=strlen($s); $i++){
   if ($a[$i-1] == is a letter){
      echo $a[$i-1]." is a letter";
   } else {
      echo $a[$i-1]." is a number";
   }
}

Is it possible to use a regular expression on the whole string instead of iterating over each character? — Tobias Nilsson, Jan 09 '13 at 08:26
Check http://stackoverflow.com/q/9721636/1169798 and http://php.net/manual/en/function.is-numeric.php — Sirko, Jan 09 '13 at 08:26

score 19 · Answer 1 · edited May 28 '16 at 14:35

19

You can use:

ctype_digit

and

ctype_alpha

edited May 28 '16 at 14:35

HenningCash

1,711
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answered Jan 09 '13 at 08:28

codaddict

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score 18 · Accepted Answer · edited Sep 14 '18 at 15:17

18

To test if character is_numeric, use:

is_numeric($a[$i-1])

As below:

$s = "rfewr545 345b";
for ($i = 0; $i < strlen($s); $i++){
   $char = $s[$i];
   if (is_numeric($char)) {
      echo $char . ' is a number';
   } else {
      echo $char . ' is a letter';
   }
}

edited Sep 14 '18 at 15:17

Dika

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answered Jan 09 '13 at 08:27

hsz

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14

Not every char that is not numeric is a letter!! – m4t1t0 Jan 09 '13 at 08:29
1

What about multibyte chars ? – Glavić Jan 09 '13 at 08:40

score 4 · Answer 3 · answered Jan 09 '13 at 08:33

4

With regular expressions you can try the following.

Test for a number

if (preg_match('/\d/', $char)) :
     echo $char.' is a number';
endif;

Test for a "letter"

if (preg_match('/[a-zA-Z]/', $char)) :
     echo $char.' is a letter';
endif;

The benefit of this approach is mainly from the "letter" test, which lets you efficiently define what constitutes as a "letter" character. In this example, the basic English alphabet is defined as a "letter".

answered Jan 09 '13 at 08:33

Boaz

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preg_match('/^[a-zA-Z\s\,]+$/') – Arun Killu Jan 09 '13 at 08:40
I believe OP refers to testing a single *letter* character, not *words*. – Boaz Jan 09 '13 at 08:42

score 0 · Answer 4 · answered Jan 09 '13 at 08:28

0

See this: http://php.net/manual/en/function.is-numeric.php

if(Is_numeric($char)) {
//Do stuff
}
else {
//Do other stuff
}

answered Jan 09 '13 at 08:28

Tikkes

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score 0 · Answer 5 · answered Jan 09 '13 at 08:28

0

You can do by using is_numeric() function

if (is_numeric($a[$i-1])){
      echo $a[$i-1]." is a number";
   } else {
      echo $a[$i-1]." is a letter";
   }

answered Jan 09 '13 at 08:28

Edwin Alex

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score 0 · Answer 6 · answered Jan 09 '13 at 08:35

0

php provide some nice function to checkout chars. Use the apt functions as conditions in if blocks.

visit:

PHP char functions

e.g. ctype_digit returns true if number is numeric.

answered Jan 09 '13 at 08:35

Sumit Malik

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score 0 · Answer 7 · answered May 28 '16 at 12:32

You may use ctype_alpha to check for alphabetic character(s).

Similarly, you may use ctype_digit to check for numeric character(s).

is_numeric — Finds whether a variable is a number or a numeric string

is_numeric() example:

<?php

    $tests = array(
        "42",
        0b10100111001,
        "not numeric",
        array(),
        9.1
    );

    foreach ($tests as $element) {
        if (is_numeric($element)) {
            echo "'{$element}' is numeric", PHP_EOL;
        } else {
            echo "'{$element}' is NOT numeric", PHP_EOL;
        }
    }
?>

The above example will output:

'42' is numeric
'1337' is numeric
'not numeric' is NOT numeric
'Array' is NOT numeric
'9.1' is numeric

Where ctype_digit() and is_numeric() differ?

Example comparing strings with integers:

<?php
    $numeric_string = '42';
    $integer        = 42;

    ctype_digit($numeric_string);  // true
    ctype_digit($integer);         // false (ASCII 42 is the * character)

    is_numeric($numeric_string);   // true
    is_numeric($integer);          // true

?>

How can I check if a char is a letter or a number?

7 Answers7

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