php string start with
How to check if a string starts with a specified string? [duplicate]
5 Answers 5
PHP 8 or newer:
PHP 7 or older:
Use the substr function to return a part of a string.
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.
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.
There is also the strncmp() function and strncasecmp() function which is perfect for this situation:
The advantage over the substr() approach is that strncmp() just does what needs to be done, without creating a temporary string.
You can use a simple regex (updated version from user viriathus as eregi is deprecated)
or if you want a case insensitive search
Regexes allow to perform more complex tasks
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).
verify, if the string starts with given substring
How can I verify if it starts with some word?
When I wrote the following script returns yes
BUT it returns yes even when I wrote
I think strpos returns zero if it can’t find substring too (or a value that evaluates to zero).
So, what can I do if I want to verify if word is in the start of string? Maybe I must use === in this case?
10 Answers 10
You should check with the identity operator (===), see the documentation.
As @Samuel Gfeller pointed out: As of PHP8 you can use the str_starts_with() method. You can use it like this:
PHP does have 2 functions to verify if a string starts with a given substring:
So if you want to test only http (and not https), you can use:
as == will turn positive for both false & 0 check the documentation
Is a bit more performant than strpos
Starting with PHP 8 (2020-11-24), you can use str_starts_with:
PHP 8 has now a dedicated function str_starts_with for this.
There’s a big red warning in the documentation about this:
This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or «». Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.
Not the answer you’re looking for? Browse other questions tagged php or ask your own question.
Related
Hot Network Questions
Subscribe to RSS
To subscribe to this RSS feed, copy and paste this URL into your RSS reader.
site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. rev 2021.9.17.40238
By clicking “Accept all cookies”, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy.
Строковые функции PHP
В этой главе будут рассмотрены некоторые часто используемые функции для работы со строками.
PHP функция strlen() возвращает длину строки.
Пример
Вернуть длину строки «Hello world!»:
PHP функция str_word_count() считает количество слов в строке.
Пример
Подсчитать количество слов в строке «Hello world!»:
PHP функция strrev() переворачивает строку.
Пример
Перевернуть строку «Hello world!»:
PHP функция strpos() ищет определенный текст в строке. Если совпадение найдено, функция возвращает позицию символа первого совпадения. Если совпадений не найдено, возвращается FALSE.
Пример
Поиск текста «world» в строке «Hello world!»:
PHP функция str_replace() заменяет некоторые символы другими символами в строке.
Пример
Заменить текст «world» на «Dolly»:
Полный справочник PHP Строки
Для полной справки на все строковые функции, перейдите к полному Справочнику PHP Строки на нашем сайте W3Schools на русском.
Справочник PHP Строки содержит описание и пример использования для каждой функции!
PHP Упражнения
ПАЛИТРА ЦВЕТОВ
ПРИСОЕДИНЯЙТЕСЬ!
Получите ваш
Сертификат сегодня!
Связь с админом
Если вы хотите сообщить об ошибке, а также внести предложение о работе сайта, добавить объявление или рекламу на сайт, не стесняйтесь отправить админу электронное письмо на email:
Топ Учебники
Топ Справочники
Топ Примеры
Веб Сертификаты
Этот сайт оптимизирован для обучения и тестирования. Примеры могут быть упрощены для улучшения чтения и базового понимания. Учебные пособия, ссылки и примеры постоянно пересматриваются, чтобы избежать ошибок, но мы не можем гарантировать полную правильность и работоспособность всего контента. Используя этот сайт, вы соглашаетесь с тем, что прочитали и приняли условия использования, cookie и политику конфиденциальности.
Также вы можете абсолютно бесплатно скачать офлайн версию сайта W3Schools на русском архивом с GitHub и пользоваться локально на своём компьютере.
Также доступна версия сайта W3Schools на украинском языке.
Copyright 1999-2021 by Refsnes Data. All Rights Reserved.
Сайт работает на фреймворке W3.CSS.
PHP Strings
A string is a sequence of characters, like «Hello world!».
PHP String Functions
In this chapter we will look at some commonly used functions to manipulate strings.
The PHP strlen() function returns the length of a string.
Example
Return the length of the string «Hello world!»:
The PHP str_word_count() function counts the number of words in a string.
Example
Count the number of word in the string «Hello world!»:
The PHP strrev() function reverses a string.
Example
Reverse the string «Hello world!»:
The PHP strpos() function searches for a specific text within a string. If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE.
Example
Search for the text «world» in the string «Hello world!»:
Tip: The first character position in a string is 0 (not 1).
The PHP str_replace() function replaces some characters with some other characters in a string.
Example
Replace the text «world» with «Dolly»:
Complete PHP String Reference
For a complete reference of all string functions, go to our complete PHP String Reference.
The PHP string reference contains description and example of use, for each function!
PHP Exercises
We just launched
W3Schools videos
COLOR PICKER
LIKE US
Get certified
by completing
a course today!
CODE GAME
Report Error
If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:
Thank You For Helping Us!
Your message has been sent to W3Schools.
Top Tutorials
Top References
Top Examples
Web Courses
W3Schools is optimized for learning and training. Examples might be simplified to improve reading and learning. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using W3Schools, you agree to have read and accepted our terms of use, cookie and privacy policy.
Type casting/juggling didnt get me anywhere (put the whole string as one element of array), and the best solution I’ve found is simply using a for loop to construct the array. It feels like there should be something better. I mean, if you can index on it shouldn’t you be able to iterate as well?
This is the best I’ve got
A) A way to make the string iterable
B) A better way to build the character array from the string (and if so, how about the other direction?)
I feel like im missing something obvious here.
9 Answers 9
Step 1: convert the string to an array using the str_split function
Step 2: loop through the newly created array
You can check the PHP docs for more information: str_split
If your strings are in Unicode you should use preg_split with /u modifier
From comments in php documentation:
For those who are looking for the fastest way to iterate over strings in php, Ive prepared a benchmark testing.
The first method in which you access string characters directly by specifying its position in brackets and treating string like an array:
I myself thought the latter is the fastest method, but I was wrong.
As with the second method (which is used in the accepted answer):
This method is going to be faster cause we are using a real array and not assuming one to be an array.
Calling the last line of each of the above methods for 1000000 times lead to these benchmarking results:
Using string[i]
0.24960017204285 Seconds
Using str_split
0.18720006942749 Seconds
Which means the second method is way faster.