How to check if a string starts with a specified string

Question

I m trying to check if a string starts with http  How can I do this check    string1    google com    string2    http   www google com

User · Answer

You can use a simple regex  updated version from user viriathus as eregi is deprecated   if  preg match    http     url      1           Starts with http  case sensitive       or if you want a case insensitive search  if  preg match    http i    url      1           Starts with http  case insensitive       Regexes allow to perform more complex tasks  if  preg match    https     i    url      1           Starts with http    or https     case insensitive       Performance wise  you don t need to create a new string  unlike with substr  nor parse the whole string if it doesn t start with what you want  You will have a performance penalty though the 1st time you use the regex  you need to create compile it       This extension maintains a global per-thread cache of compiled regular   expressions  up to 4096     http   www php net manual en intro pcre php

User · Answer

Use strpos     if  strpos  string2   http       0          It starts with  http      Remember the three equals signs        It will not work properly if you only use two  This is because strpos   will return false if the needle cannot be found in the haystack

User · Answer

PHP 8 or newer  Use the str starts with function  str starts with  http   www google com    http    PHP 7 or older  Use the substr function to return a part of a string  substr   string n  0  4        quot http quot   If you re trying to make sure it s not another protocol  I d use http    instead  since https would also match  and other things such as http-protocol com  substr   string n  0  7        quot http    quot   And in general  substr  string  0  strlen  query        query

User · Answer

There is also the strncmp   function and strncasecmp   function which is perfect for this situation   if  strncmp  string n   http   4      0    In general   if  strncmp  string n   prefix  strlen  prefix       0    The advantage over the substr   approach is that strncmp   just does what needs to be done  without creating a temporary string

User · Answer

You can check if your string starts with http or https using the small function below   function has prefix  string   prefix       return substr  string  0  strlen  prefix       prefix      url      http   www google com   echo  the url      has prefix  url   http          does     does not       start with http      echo  the url      has prefix  url   https         does     does not       start with https

[php] How to check if a string starts with a specified string?

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