Reprint-php Questions

1. Write the results of the following code:
$a = "Hello world!";
$b = $a;
Print ("\ $b = $b
");
Print (' $a = $a
');
?>

$b =hello world!
$a = $a
' \ ' is a escape character that masks the special use of a single special character immediately following it
' Single-quote pairs, shielding the special meanings of almost all special characters included, in addition to itself
Also, debug the code at the command line,
is not used as a newline output ~ If in browser, another

2. Write the following code to output the result:
$a = "First";
$b =& $a;
$c = $a;
$a = "Second";
Print ("$a, $b, $c
");
?>

Second,second,first
$b is a $ A reference assignment, so a change of $ A is a $b change.
$c can be seen as a $ A copy once, so it is irrelevant to the two variables, so the $a change does not affect $c

3. Write the following code to output the result:
$a = 2;
$b = "1.2SBC3";
$c = "EFG";
$result 1= $a. $b;
$result 2= $a * $b;
$result 3= $a * $c;
Print ("$result 1, $result 2, $result 3
");
?>

21.2sbc3,2.4,0
$result 1 is a string connection, btw, if this question is 2. $b, the system will report the error
$result 2 is a multiplication of numbers, and PHP automatically discards the characters that follow the first character that is not a number.
$result 3 is the multiplication of numbers, unlike 2, there is no numeric character in the $c, so the whole is forcibly converted to a numeric type, which is 0, and then multiplied with $a=2, and the final result is 0.

4. The following incorrect variable names are:
A. $_test B. $2abc c. $Var D. $%var

B

5. Statement for ($k =0; $k =1; $k + +), and statement for ($k =0; $k ==1; $k + +); The number of executions is:
A. Infinity and 0 B. 0 and Infinity C. Are infinitely D. are all 0

A

/**
* Here to focus on this question, here to choose a should be no problem, everyone knows
The question is, if the first sentence is changed into a for ($k =0; $k =0; $k + +), then how many times does the loop experience be executed?
*
* The answer is 0.
*
* The reason is that for (expr A; expr b; expr C) We are concerned about the true value of the expression expr B when judging whether to execute the loop body.
Note $k =0 The value of this expression is 0! Instead of a possible replication, the 1 returned successfully!
* Therefore, the loop for the for loop to determine the condition is permanent, nature will not execute the loop body ~ ~ ~
*
* ：）
**/


6. Features not supported by PHP functions are:
A. Variable function name b. variable number of arguments c. passing parameters by reference
D. Passing parameters by pointer E. Implementing recursive functions

D

7. The following description of the classes in PHP is not correct:
A. Support for single inheritance B. Support for multiple inheritance C. Constructors not supported D. Destructors are not supported
E. You must use the $this pointer to refer to the member variable

b Multiple inheritance seems to be using the interface

8. Locate the error in the following code and fix it:
$a [0]= "" Ryan;
$b ["Value"]=785.9;
$c ["Blue"][0]= "Ada";
Print ("$a [0], $b [" value "], $c [" Blue "][0]
");
?>

$a [0]= "Ryan";
$b ["Value"]=785.9;
$c ["Blue"][0]= "Ada";
Print ("$a [0]". " $b [value] "." {$c [blue][0]} "."
");
?>

Quotes, nothing to say.
Also the key is the last line of $c[blue][0], if not enclosed in curly braces, then the system will automatically replace the variable $c[blue], the problem is that the value does not exist, so, after the replacement of Xxxx[0] will not have, so will error. This is called an array of variables.


9. Write down the precedence of the following operators in order from highest to lowest:
and,=,>,+,~

~ + > = and I guess

10. The difference between isset () and Empty ()


Isset ()
Test whether a variable exists

Empty ()
Test whether the variable is empty

In a language that is not strictly defined for variables such as PHP
If a variable has never been declared, then Isset==false|empty==true
If a variable is declared, but the assignment is null, as in the previous case
If a variable is declared but assigned a value of ', then isset==true|empty==true
If a variable is declared and is assigned a normal value, then Isset==true|empty==false

Example as follow:
$b = NULL;
$c = ";
$d = ' str ';
echo isset ($a). " A\n ";
echo empty ($a). " B\n ";
echo isset ($b). " C\n ";
echo Empty ($b). " D\n ";
echo isset ($c). " E\n ";
echo Empty ($c). " F\n ";
echo isset ($d). " G\n ";
echo Empty ($d). " H\n ";
?>

11. Please use as few statements as possible to verify the input email address of the function.

Eregi (' ^[_a-z0-9]+ (\.[ _a-z0-9-]+) *@[a-z0-9]+ (\.[ a-z0-9-]+) *$ ', $emailaddress)

12. Write an algorithm, sort the following array in ascending order, and write out the sort algorithm name:
$arrVar =array (64,29,1,43,30,9,39,75,4,11)

Bubble sort, process slightly

13. Write a program that converts the first letter of each word in the text file to uppercase and saves it back to the original file.
Tip: Convert the first letter of the word in a string to an uppercase function: String ucwords (String str)



14. Please write down several ways that PHP accesses MySQL database, and do a brief introduction.

15. Please write out the implementation method of Phpsession, and describe the best way to implement it, and explain the reason.
Hint: The way of SessionID, the storage method of session variable and so on.

What are the vulnerabilities of the PHP program?

I am the biggest loophole ...


Do not know right ~ ~ Hehe ~ ~ found the concept of something is still quite tangled ~ ~
The word more slowly again write ~ ~ ~:)

