PHP-strpos未检查第一个单词

Question

I'm trying to do some validation in PHP, and one of them is checking whether there is a specific word in the inputted string or not. The problem is, my code seem to not working when I put the specified word first.

here's the code:

$word = "aa bb cc dd";
if(strpos($word, 'aa') == false)
{
    echo "wrong input";
}

but if I change the $word to either bb aa cc dd or bb cc dd aa , it works. I wonder how to fix this though.

Answer 1

strpos will return false if your string isn't there. Otherwise, it returns the position of your string.

In this case, 'aa' is at the start of the string, which means that it's at position 0; and 0 evaluates to false.

You need to do a boolean compare on the result:

if(strpos($word, 'aa') === false)

Answer 2

That's because strpos returns the position of the word, in this case 0. 0 is falsey. == does not check for identical matches, === does. So use a triple equals.

It's even in the docs .

Answer 3

strpos is returning 0, as 'aa' is the 0th character. As 0 == false but does NOT === false (it is not boolean), you need to use === instead of == .

Answer 4

You should use the strict comparison operator, this will match against the same type, so using === will check if it's a Boolean:

if(strpos($word, 'aa') === false)
{
    echo "wrong input";
}

Using == is a loose comparison, anything can be stated true (apart from true , 1 , string ), eg

"false" == false    // true
"false" === false   // false

The reason why it's false because it's comparing a string against a Boolean which returns false.

Answer 5

Because the position of aa is 0, which equals to false .

You have to use: if(strpos($word, 'aa') === false)

Answer 6

Add a space before search string and find more than 0 position

if(strpos(" ".$word, 'aa') > 0)
{
    echo "Found it!";
}