How to check if data is empty or whitespace only in PHP

问题

I have an input field that needs a username. The scenario is, how can i prevent user from providing whitespace or whitespaces in the that field? I already added required in the input field so i can prevent user from leaving it blank.

<input type="text" name="username" required>

but what if the user puts whitespace or as many whitespace as he can, is there any possible way i can detect this and throw error to the user?

in my php file i already have

if(empty($_POST['username'])){
echo "Username should not be empty!";
}

but this will fail because of the whitespaces the users put in the input field.

回答1:

You could do like this.

if(isset($_POST['username']))
{
    if(strlen(trim($_POST['username']))<=0){
    echo "Username should not be empty!";
    }
}

回答2:

You can use trim and strlen php functions

回答3:

Try This....

if( trim($_POST['username']) == ""){
     echo "Username should not be empty!";
}

回答4:

u can use $.trim() jquery function before to submit form.

var nowhitespace = $.trim($("#input").val());

回答5:

I think str_replace() is all you want. Or you could some javascript to prevent whitespace from being entered into the input field.

<?php
$s = str_replace(' ', '', $_POST['username']);
?>

If you're going to use trim(), don't forget about rtrim()

来源：https://stackoverflow.com/questions/21709682/how-to-check-if-data-is-empty-or-whitespace-only-in-php