PHP stuff pt. 1
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Created by:
sharkjohnson on July 22, 2010
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Description:
so I got a book and I want to learn it up.
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46 terms
Terms | Definitions |
|---|---|
 set of rules that dictate how you write programs in a language. | Lexical Structure |
| are function names case-sensitive? | no |
| are class names case-sensitive? | no |
| what class name is reserved? | stdClass |
| how do you make a constant and echo it? | define('Truth', 'Mark'); echo Truth; |
| what's a synonym for a reserved word? | a keyword |
| floating point number | numbers with decimal digits |
| how can you test to see if a number has decimal digits? | is_float() |
| what do you call variables in classes? | properties |
| how do you create a new object? | $obj = new Class ($ed = new Person) |
| a resource is... | a handle is ... |
| where do you really see the benefit of automatic cleanup of the $dbc handle? | when it's a local variable (in a function). then it disappears when the function ends. |
| is NULL case-sensitive? | no |
| how do you test if a $var has been initiated with null? | if ($unititiated_Var === null) echo 'yea'; |
| how can you make a value in a variable a variable itself with its own value? | $foo = 'bar'; $$foo = 'baz'; now $bar = 'baz' |
| how do you make a variable reference for $white? | $black =& $white; now $black's value will always be $white's (and vise-vera). You can also do this sort of thing with functions (but it's a little weirder) |
| what's the relationship between local and global functions of the same name? | they are totally isolated from each other. |
| what is a static variable? | a variable that retains its value between calls to a function (but is still local) |
| what is a symbol table? | an array that maps variable names to the positions of their values in memory. |
| how does PHP save memory when you write $var1 = $var2? | Instead of copying the data from $var2 into $var1, it updates the symbol table to say "both of these variables represent the same chunk of info". It only makes a copy when you change some info in one of the variables. |
| what is "copy-on-write"? | Instead of copying the data from $var2 into $var1, it updates the symbol table to say "both of these variables represent the same chunk of info". It only makes a copy when you change some info in one of the variables. |
| what's a reference count? | the number of ways to reference a particular value (this number is also stored in a symbol table) |
| what can decrease a reference count? (2 examples) | 1) if a variable goes out of scope 2) if you change something in a $var1 so $var2 (it's 'copy') becomes different. (there are others) |
| what happens if a variable's reference count reached 0? | it's memory is released. |
| how can you free a variable's memory manually? | unset() |
| what is operator associativity using 2/2*2 as an example? | If two operators have the same precedence (like '/' and '') then associativity determines which terms we evaluate first. / and are left-to-right, we calculate this expression as (2/2)*2 |
| what is casting? | the conversion of one type of a value to another type. |
| type juggling | implicit casting (conversion of one type of a value to another type) via arithmetic operations (like if a string is the second operand and an integer or floating point is the first, then the string type will be converted to match) |
| how does PHP calculate the numeric value of strings? (2) | 1) if no number is found at the beginning of the string, then its numeric value is 0 2) if is contains a '.' or an 'e'/'E', then any number in it will evaluate as a floating-point number |
| what is "9 Lives" - 1? | 8 (int) |
| what is "3.14 Pies" * 2 | 6.28 (float) |
| what is "9 Lives." - 1 | 8 (float) |
| what is "1E3 Points of Light" + 1 | 1001 (float) |
| how do you convert an array ($a) to an object ($o)? | $o = (object) $a; |
| how do you quickly add 5 to a variable? | $a +=5; |
| how do you end a "while" loop early? | break; |
| how do you end a "while" loop as well as the other "while" loops it (may be) buried within? | break 2 (where "2" is the number of loop levels. |
| how do you stop an inner loop early but let the outer loop keep going? | continue 2 (where "2" is the # of loop levels) |
| how do you write $counter = 0; while ($counter < 10) { echo "counter is $counter\n"; $counter++;} as a "for" statement? | for ($counter = 0; $counter < 10; $counter++) { echo "counter is $counter\n"; } |
| what are loop expressions? | 1. while 2. do/while 3. for 4. foreach |
| can you use "break" and "continue" with a "for" loop? | yes! |
| when do you use "foreach"? | when you want to iterate over elements in an array. |
| what is structure of "foreach"? | foreach ($array as $current) or ($result as $row) |
| what is the "foreach" structure to use when you want to access both key and value? | foreach ($array as $key->$value) |
| how do you execute some_function() after every third statment in a loop is executed? | register_tick_funtion("some_function"); declare(ticks = 3) {for($i=0; $i<10; $i++){...}} |
| do you need parenthesis with "include"? | no! |
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