It is once again the world’s most valuable company by market capitalization (share price times number of shares outstanding).

Apple’s market cap was boosted by a $56 (14%) surge in July, a gain that was softened by a stock repurchase plan that reduced its number of outstanding shares in fiscal Q3 by 23.5 million.

Exxon was hurt by falling oil prices and a disappointing earnings report.

The two companies have changed leads many times before. See here, here, here, here, and here,