I was running the following PHP code using addition?

Question

this is code:

    <?php
    $a = "4 fox and 3 cows"; // it is simple string
    $b = 22;
    echo $ab = $a + $b;
    echo "output::".$ab;
    ?>'

output: only first index is being read 26 what is the logic behind this..? instead I should get an error..

2.another example:

     <?php
        $a = "four fox and 3 cows"; // it is simple string
        $b = 22;
        echo $ab = $a + $b;
        echo "output::".$ab;
        ?>'
   output:
   22
   what is the logic behind this..?

`$a` is converted to an int by truncating everything that is not part of a valid int. 4+22 = 26. — AbraCadaver, Jun 18 '15 at 18:21
Why should you get an error? When you perform addition on a string, PHP attempts to turn the strings into integers first. In this case, it sees `4` at the start of your string, and discards the rest. (If there's no valid number at the start of the string, it becomes 0). So 22 + 4 is 26. — andrewsi, Jun 18 '15 at 18:21
String concatenation is in the manual : http://php.net/manual/en/language.operators.string.php - should have really been your first port of call IMO. — CD001, Jun 18 '15 at 18:24
@everyone_talking_about_concatenation OP didn't say anything about wanting to concatenate the strings. — iam-decoder, Jun 18 '15 at 18:25
I love that these types of questions always get like 4+ answers... — castis, Jun 18 '15 at 18:25

iam-decoder · Answer 1 · 2015-06-18T18:31:02.010

4

You should look into Type Juggling, php does it's best to accommodate the ability to transform type casting on the fly, using the + operator in php is meant for 2 numbers whether they are integer, decimal, etc.

Since strings don't have an integral value, when you use the + operator it will use the first part of the string that can make up a valid integer.

Since your example starts with "4 " it truncates everything else and turns the 4 into an integer making it 4+22 which is 26.

edited Jun 18 '15 at 18:31

answered Jun 18 '15 at 18:22

iam-decoder

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For this to be a good answer you should at least call it by its name: type juggling. It's an important thing to know in PHP. – John Conde Jun 18 '15 at 18:27

score 0 · Answer 2 · answered Jun 18 '15 at 18:23

0

Use the . operator to concatenate strings.

The + operator will convert the strings to numerics and add them

answered Jun 18 '15 at 18:23

Alexandre

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i dont think he's after string concatenation – iam-decoder Jun 18 '15 at 18:23
It is not clear at all what that code is supposed to do. Just giving some pointers. – Alexandre Jun 18 '15 at 18:25
@iam-decoder that was what I was thinking, but couldn't possibly try to add the string as a number with another number. Probably was just an example or something. – Evan Carslake Jun 18 '15 at 18:26
1

Also, that is why I upvoted this and the above (just to counter the -1's.) – Evan Carslake Jun 18 '15 at 18:26
thankyou @Evan Carslake for your support... – Muhammad Ahsen Haider Jun 18 '15 at 18:34

score 0 · Answer 3 · answered Jun 18 '15 at 18:23

If you wanted to concat the number with the string, the operator in php is ., not +.

otherwise, why would you want to add a number with a string? What result did you expect? It seems in these case php parses the string to int, ignoring everything that comes after the number it can understand.

score 0 · Answer 4 · answered Jun 18 '15 at 18:24

0

+ just converts your string to int, stripping everything unknown to a number.

"4 fox and 3 cows"

^^> everything there gets stripped, because a number can't be processed of fox and 3 cows, php reads the number from left to right and once it meets something weird, it stops.

answered Jun 18 '15 at 18:24

nicael

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Not exactly true. It's type juggling at work. – John Conde Jun 18 '15 at 18:24
@John So? What's incorrect, still? – nicael Jun 18 '15 at 18:26

I was running the following PHP code using addition?

4 Answers4