These are ten commands that you really need to know in order to get started with UNIX. They are probably similar to commands you already know for another operating system. 

Command	Example	Description
1.     ls	ls ls -alF	Lists files in current directory List in long format
2.     cd	cd tempdir cd .. cd ~dhyatt/web-docs	Change directory to tempdir Move back one directory Move into dhyatt's web-docs directory
3.     mkdir	mkdir graphics	Make a directory called graphics
4.     rmdir	rmdir emptydir	Remove directory (must be empty)
5.     cp	cp file1 web-docs cp file1 file1.bak	Copy file into directory Make backup of file1
6.     rm	rm file1.bak rm *.tmp	Remove or delete file Remove all file
7.     mv	mv old.html new.html	Move or rename files
8.     more	more index.html	Look at file, one page at a time
9.     lpr	lpr index.html	Send file to printer
10.   man	man ls	Online manual (help) about command

Its pretty easy to find out if a string exists in another string in PHP. There are predefined functions provided by PHP to do this job.

Using strpos - 

echo strpos("I love php, I love php too!","php");

Output: 7

 The strpos() function finds the position of the first occurrence of a string inside another string.

Explode — Split a string by string

Syntax:
array explode ( string $delimiter , string $string [, int $limit ] )

To remove empty elements after explode,

array_map('trim', explode(",", $myString));

The below basic shortcut keys are a listing of shortcut keys that will work with almost all IBM compatible computers and software programs. It is highly recommended that all users keep a good reference of the below shortcut keys or try to memorize the below keys. Doing so will dramatically increase your productivity.

Shortcut Keys	Description
Alt + F	File menu options in current program.
Alt + E	Edit options in current program
F1	Universal Help in almost every Windows program.
Ctrl + A	Select all text.
Ctrl + F	Open find window for current document or window.
Ctrl + S	Save current document file.
Ctrl + X	Cut selected item.
Shift + Del	Cut selected item.
Ctrl + C	Copy selected item.
Ctrl + Ins	Copy selected item
Ctrl + V	Paste
Shift + Ins	Paste
Ctrl + P	Print the current page or document.
Home	Goes to beginning of current line.
Ctrl + Home	Goes to beginning of document.
End	Goes to end of current line.
Ctrl + End	Goes to end of document.
Shift + Home	Highlights from current position to beginning of line.
Shift + End	Highlights from current position to end of line.
Ctrl + Left arrow	Moves one word to the left at a time.
Ctrl + Right arrow	Moves one word to the right at a time.