Check if string is just white space?

Question

Possible Duplicate:
If string only contains spaces?

I do not want to change a string nor do I want to check if it contains white space. I want to check if the entire string is ONLY white space. What the best way to do that?

@Dan McG I must suck at searching because I swear I searched for this before I posted it. — JD Isaacks, Jun 07 '10 at 19:17
@webbiedave The answers are similar. How many ways do you need to check for a space white space string? — Justin Johnson, Jun 07 '10 at 19:33
@Justin Johnson: So if someone comes up with a better way to do it, it shouldn't be added or upvotable? — webbiedave, Jun 07 '10 at 19:35
No, it should be posted on the first question. Just because a question has an answer, doesn't mean an alternate or better answer cannot be posted later. — Justin Johnson, Jun 07 '10 at 19:38
@Justin Johnson: Maybe we should throw this on meta. I'd be curious to know the consensus on this. — webbiedave, Jun 07 '10 at 19:41
My thinking is this: Duplicate questions decentralize responses and have negative effects on organization, which is why they have the option to be closed by the community (which I typically encourage in cases like this). However, I have seen questions that ask the same thing but illicit a completely different type of response where it made sense to keep both questions open (looking for link), but this is not one of those. Rep is nice, but to me it comes second to the organization and consistency of the resource that this community is building. — Justin Johnson, Jun 07 '10 at 19:50
Also, the rep that you got for your answer wont go away if the question is closed (99% sure of that), so it doesn't really hurt those who have answered. — Justin Johnson, Jun 07 '10 at 19:52
Rep only disappears on deleted questions. BTW, the question sited as an exact dup asks about detecting *spaces*, not *white space*. So the question is not an **exact** duplicate. — webbiedave, Jun 07 '10 at 20:06
Plus, neither this question nor the other has an answer taking into account Unicode whitespace (preg_match('/^[\pZ\pC]$/u',$str)). Very lame indeed to close just because it seems that it might be a duplicate, while in reality there is just a vague analogy. — Unai Vivi, Nov 15 '12 at 23:45

webbiedave · Accepted Answer · 2010-06-07T19:21:55.427

130

This will be the fastest way:

$str = '      ';
if (ctype_space($str)) {

}

Returns false on empty string because empty is not white-space. If you need to include an empty string, you can add || $str == '' This will still result in faster execution than regex or trim.

ctype_space

edited Jun 07 '10 at 19:21

answered Jun 07 '10 at 19:16

webbiedave

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Wow, I didn't imagine it could get much simpler than the trim, but I guess it can. +1 for a function I've never seen or used. – Matt Brunmeier Jun 07 '10 at 19:21
2

Check out: http://php.net/manual/en/book.ctype.php Check for alphanumeric character(s) ctype_alpha — Check for alphabetic character(s) ctype_cntrl — Check for control character(s) ctype_digit — Check for numeric character(s) ctype_graph — Check for any printable character(s) except space ctype_lower — Check for lowercase character(s) ctype_print — Check for printable character(s) ctype_punct — Check for any printable character which is not whitespace or an alphanumeric character ctype_space — Check for whitespace character(s) ctype_upper — Check for upperca... – Cas Bloem Sep 16 '14 at 08:26
"This will still result in faster execution than regex or trim." < True; http://ideone.com/t8ou8D – Cas Bloem Sep 16 '14 at 08:43
`ctype_space(" ") === false` – gondo Oct 31 '16 at 15:56
1

if empty check is needed, use `if (ctype_space($str . ' '))` – Divins Mathew Jan 24 '21 at 14:07

score 49 · Answer 2 · answered Jun 07 '10 at 19:08

49

since trim returns a string with whitespace removed, use that to check

if (trim($str) == '')
{
 //string is only whitespace
}

answered Jun 07 '10 at 19:08

MANCHUCK

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Hmm, indeed, faster then the preg_* route.. – Wrikken Jun 07 '10 at 19:09
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+1 for a non regex solution. Not that there is anything wrong with regex. – Neil Aitken Jun 07 '10 at 19:10
6

Just remember that trim will turn anything you pass into it into a string. i.e (trim(false) == '') will return true, which may fall outside the original poster's requirements (but it most likely fine) – Alana Storm Jun 07 '10 at 19:25
Can be done faster > http://ideone.com/t8ou8D – Cas Bloem Sep 16 '14 at 08:43

score 13 · Answer 3 · answered Jun 07 '10 at 19:08

13

if( trim($str) == "" )
    // the string is only whitespace

This should do the trick.

answered Jun 07 '10 at 19:08

svens

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score 5 · Answer 4 · answered Jun 07 '10 at 19:08

5

preg_match('/^\s*$/',$string)

change * to + if empty is not allowed

answered Jun 07 '10 at 19:08

Wrikken

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What does `\s` mean? Non white space? – JD Isaacks Jun 07 '10 at 19:12
@John, as said, whitespace, perhaps your confusing the character class ^ ([^p] = anything not 'p') with '^p' (= string has to start with p) – Wrikken Jun 07 '10 at 19:25
`\s` is "whitespace," `\S` is "not whitespace" – Justin Johnson Jun 07 '10 at 19:36
I'm voting down only because you should avoid regex only when needed. For something simple as this, build in PHP functions are the way to go – MANCHUCK Jun 07 '10 at 19:48
@Wrikken, yes thanks. I have never used the \s char, plus I think regex is much easier to write than to read. – JD Isaacks Jun 07 '10 at 20:15
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@MANCHUCK: I even voted myself down & ctype_space up, but there were already comments here so I opted not to delete it. – Wrikken Jun 07 '10 at 21:26

Check if string is just white space?

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