preface ：PHP Is a general open source scripting language , Various functions will be encountered in both the development process and the interview process , Today, let's sort out the commonly used functions .

character string （string） function

strlen： Get string length , bytes substr_count：  Count the number of times a substring appears in a string substr： String interception , Get string （ Intercept by byte ）strchr： And substr be similar , Intercept from the specified location until the end strrchr（ Get file suffix ）： And strchr equally , Just start looking for characters from the right strtolower： All characters are lowercase （ For English letters ）strtoupper： All characters are capitalized strrev： String inversion （ Can only reverse English ： English storage has only one byte ）, Reverse by byte strpos： Find the position of the corresponding character from the string （ Numeric subscript ）, Start from the far left strrpos： And strpos equally , Just start from the right side of the string trim： Remove the characters on both sides of the function , Default is space str_split  The function splits a string into an array .chunk_split：  Break the string into a series of smaller parts str_repeat： Repeat the string a specified number of times str_replace： Replace some characters in a string （ Case sensitive ）ucfirst ： Convert the first character of a string to uppercase 

date （date） function

time： Returns the... Of the current time  Unix  Time stamp date： Format local date and time strtotime： Parse the date or time description of any English text into  Unix  Time stamp microtime： Returns the current  Unix  The microseconds of the timestamp 

Numbers （math） function

abs： The absolute value floor： Rounding down ceil： Rounding up round： rounding rand： Gets a random integer in the specified range mt_rand： Gets a random integer in the specified range （ More efficient ）min: Returns the smallest value in an array , Or the smallest of several specified values max: Returns the maximum value in an array , Or the maximum of several specified values 

Array （array） function

count： Returns the number of elements in the array key： Get the key name from the associated array current： The current pointer obtained points to the value of the element next： Get the value of the next element , And move the pointer down prev： Get the value of the previous element , And move the pointer up end ： Move the pointer to the last element of the array , And return the value of the final pointer position reset： Move the pointer to the first element of the array , Returns the value of the final pointer position array_keys： Get all the key names of an array , Returns an index array array_values： Get all the values of an array , Returns an index array explode： Break a string into an array implode： Returns a string composed of array elements join： implode()  Another name for array_merge： Combine one or more arrays into an array array_reverse ：  Returns the inverted array array_flip ：  Swap keys and values in an array array_shift： Pop up elements from the front of the array , Get the value of the element array_pop： Pop up elements from the back of the array , Get the value of the element array_unshift： Push in elements from the front of the array , Get the number of current array elements array_push： Push in elements from the back of the array , Get the number of current array elements 

Judgment function

is_bool： Determine whether it is Boolean is_float： Determine whether it is floating point is_integer： Determine whether it is an integer is_object： Judge whether it is the object is_array： Determine if it's an array is_string： Whether the string is is_resource： Determine if it's a resource is_null ： Check whether the variable is NULLis_numeric： Judge the string composed of numbers or pure numbers isset： Judge whether it is defined 

summary

The functions listed above are only a common part , Interested friends can search “ Novice tutorial ” Go and check the relevant PHP course .

I'm a small program software developer , Share the knowledge points encountered in the development process every day , If it helps you , Give me a favor before you go , Thank you very much .

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