CODEWITHSUNDEEP
phpstringstrpos
Marc
Marc

Reputation: 746

strpos() in ternary expression unexpectedly executes false branch when finding a match at the start of the string

I am trying to use PHP's strpos() function to search for a string within another string. I have performed 2 different searches, both containing a colon character. The only difference I can see between the two is whether the colon appears at the beginning of the 'needle' or the end.

My code is as follows:

<?php
$string = 'abc:def';
echo strpos($string,'abc:') ? 'abc: true' : 'abc: false';
echo ' / ';
echo strpos($string,':def') ? ':def true' : ':def false';

The output I am getting is abc: false / :def true. I don't understand why, and was hoping someone can explain it to me. You can see a working example here:

http://ideone.com/MyEn5d

Upvotes: 0

Views: 452

Answers (4)

mareckmareck
mareckmareck

Reputation: 1580

Strpos returns the position of a given string (needle) in other string (stack). See reference - strpos. Correct usage of strpos (notice it's !== not !=, since we want to also check for type):

$string = 'abc:def';
echo strpos($string,'abc:') !== false ? 'abc: true' : 'abc: false';
echo ' / ';
echo strpos($string,':def') !== false ? ':def true' : ':def false';

Summing up, strpos returns the numeric value that is a position (so for example 0 or 5) or false when the value is not found.

As to why your snippet

echo strpos($string,':def') ? ':def true' : ':def false';

returns true - in PHP every non-zero integer is treated as true, if you are comparing it as boolean, and your strpos returned value bigger than zero (probably '4' in this example), so it was considered true. See here for more details.

Upvotes: 2

Abhik Chakraborty
Abhik Chakraborty

Reputation: 44844

You need to use Boolean comparison and it returns false only when there is no match

$string = 'abc:def';
echo strpos($string,'abc:') !== false ? 'abc: true' : 'abc: false';
echo ' / ';
echo strpos($string,':def') !== false ? ':def true' : ':def false'; 

strpos($string, "abc") will return (int) 0
(int) 0 !== false ---> true statement
(int) 0 === true ---> false statement

Upvotes: 1

Rakesh Sharma
Rakesh Sharma

Reputation: 13728

In your case strpos() returning true/false result so you need to check according to return result try

echo strpos($string,'abc:') !== false ? 'abc: true' : 'abc: false';
echo ' / ';
echo strpos($string,':def') !== false ? ':def true' : ':def false';

Upvotes: 1

Awlad Liton
Awlad Liton

Reputation: 9351

as per doc

strpos()

Find the numeric position of the first occurrence of needle in the haystack string. Returns the position of where the needle exists relative to the beginning of the haystack string (independent of offset). Also note that string positions start at 0, and not 1.

so

strpos($string,'abc:')

is returning 0. so it is echoing :

abc: false

Upvotes: 1

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