PHP - 为什么这个工作而其他不工作[重复]

Question

This question already has an answer here:

• strpos issue with 0==false? 3 answers
• php 5 strpos() difference between returning 0 and false? 5 answers

Using php, I tried to check whether a certain string contains some characters.

I used this code, which evaluates to false:

$string1 = 'Hello World!';
if (strpos($string1, 'hel')) {
    echo 'True!';
}

I did a quick google search and found this variation:

$string1 = 'Hello World!';
if (strpos($string1, 'hel') !== false) {
    echo 'True!';
}

Which works and evaluates to true.

What is the actual difference between them and why the first one evaluates as false and the second as true?

Thanks!

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Answer 1

Strpos returns the position of the first letter of the needle.
In your case that is the h in "hello" at position 0.

Since typcasting is enabled in php, 0 is the same as false.
Thus the first is false because the "h" is at the 0 position of the "hello world" string