Getting the first character of a string with str 0

Question

I want to get the first letter of a string and I ve noticed that  str 0  works great  I am just not sure whether this is  good practice   as that notation is generally used with arrays  This feature doesn t seem to be very well documented so I m turning to you guys to tell me if it s all right  ndash  in all respects  ndash  to use this notation   Or should I just stick to the good ol  substr  str  0  1    Also  I noted that curly braces   str 0   works as well  What s up with that

User · Answer

Lets say you just want the first char from a part of $_POST, lets call it 'type'. And that $_POST['type'] is currently 'Control'. If in this case if you use $_POST['type'][0], or substr($_POST['type'], 0, 1)you will get C back.

However, if the client side were to modify the data they send you, from type to type[] for example, and then send 'Control' and 'Test' as the data for this array, $_POST['type'][0] will now return Control rather than C whereas substr($_POST['type'], 0, 1) will simply just fail.

So yes, there may be a problem with using $str[0], but that depends on the surrounding circumstance.

User · Answer

Yes  Strings can be seen as character arrays  and the way to access a position of an array is to use the    operator  Usually there s no problem at all in using  str 0   and I m pretty sure is much faster than the substr   method    There is only one caveat with both methods  they will get the first byte  rather than the first character  This is important if you re using multibyte encodings  such as UTF-8   If you want to support that  use mb substr    Arguably  you should always assume multibyte input these days  so this is the best option  but it will be slightly slower

User · Answer

The    syntax is deprecated as of PHP 5 3 0  Square brackets are recommended

User · Answer

In case of multibyte  unicode  strings using str 0  can cause a trouble  mb substr   is a better solution  For example    first char   mb substr  title  0  1     Some details here  Get first character of UTF-8 string

User · Answer

Speaking as a mere mortal  I would stick with  str 0    As far as I m concerned  it s quicker to grasp the meaning of  str 0  at a glance than substr  str  0  1    This probably boils down to a matter of preference   As far as performance goes  well  profile profile profile      Or you could peer into the PHP source code

User · Answer

str    abcdef   echo  str 0                      a

User · Answer

I ve used that notation before as well  with no ill side effects and no misunderstandings   It makes sense -- a string is just an array of characters  after all

User · Answer

It ll vary depending on resources  but you could run the script bellow and see for yourself      lt  php  tests   100000   for   i   0   i  lt   tests   i           string   md5 rand          position   rand 0  31         start1   microtime true        char1    string  position        end1   microtime true        time1  i     end1 -  start1        start2   microtime true        char2   substr  string   position  1        end2   microtime true        time2  i     end2 -  start2        start3   microtime true        char3    string  position        end3   microtime true        time3  i     end3 -  start3      avg1   array sum  time1     tests  echo  the average float microtime using  array    is     avg1   PHP EOL    avg2   array sum  time2     tests  echo  the average float microtime using  substr    is     avg2   PHP EOL    avg3   array sum  time3     tests  echo  the average float microtime using  array    is     avg3   PHP EOL    gt      Some reference numbers  on an old CoreDuo machine      php 1 php  the average float microtime using  array    is 1 914701461792E-6 the average float microtime using  substr    is 2 2536706924438E-6 the average float microtime using  array    is 1 821768283844E-6    php 1 php  the average float microtime using  array    is 1 7251944541931E-6 the average float microtime using  substr    is 2 0931363105774E-6 the average float microtime using  array    is 1 7225742340088E-6    php 1 php  the average float microtime using  array    is 1 7293763160706E-6 the average float microtime using  substr    is 2 1037721633911E-6 the average float microtime using  array    is 1 7249774932861E-6   It seems that using the    or    operators is more or less the same

User · Answer

My only doubt would be how applicable this technique would be on multi-byte strings  but if that s not a consideration  then I suspect you re covered   If in doubt  mb substr   seems an obviously safe choice    However  from a big picture perspective  I have to wonder how often you need to access the  n th character in a string for this to be a key consideration

[php] Getting the first character of a string with $str[0]

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